৪৯তম বিসিএস ⎯ ফলিত রসায়ন [৫৪১]

The famous novel, The Bluest Eye, is written by - American author.

• The Bluest Eye:
- এটি Toni Morrison রচিত।
- এটি একটি novel.
- এটি ১৯৭০ সালে প্রকাশিত হয়।

• Toni Morrison ছিলেন একজন আমেরিকান Novelist, essayist এবং Editor.
- তাছাড়া তিনি Princeton University এর প্রফেসর ছিলেন।

তাঁর উল্লেখযোগ্য সাহিত্যকর্ম গুলো -
- Beloved,
- Song of Solomon,
- The Bluest Eye.

Source: Britannica.

বাংলাদেশের তত্ত্বাবধায়ক সরকার:
- বাংলাদেশের তত্ত্বাবধায়ক সরকার বাংলাদেশের একপ্রকারের শাসন ব্যবস্থা, যার অধীনে দুইটি নির্বাচিত সরকারের মধ্যবর্তী সময়কালে সাময়িকভাবে অনির্বাচিত ব্যক্তিবর্গ কোন দেশের শাসনভার গ্রহণ করে থাকে।
- বিএনপি সরকারের পদত্যাগের পর ১৯৯৬ সালে ত্রয়োদশ সংশোধনের মাধ্যমে সংবিধানে যোগ হয় তত্ত্বাবধায়ক সরকার পদ্ধতি।
- এই সংশোধনীর মাধ্যমে ১৯৯৬ সালে সাংবিধানিকভাবে তত্ত্বাবধায়ক সরকার ব্যবস্থা চালু হয়।
- বিচারপতি মুহাম্মদ হাবিবুর রহমান ছিলেন সেই তত্ত্বাবধায়ক সরকারের প্রধান উপদেষ্টা।
- উপদেষ্টা পরিষদের বাকিরা হলেন: ব্যারিস্টার সৈয়দ ইশতিয়াক আহমেদ, ড. মুহাম্মদ ইউনূস, অর্থনীতিবিদ ড. ওয়াহিদউদ্দিন মাহমুদ, অধ্যাপক মো. শামসুল হক, অধ্যাপক জামিলুর রেজা চৌধুরী, শেগুফতা বখত চৌধুরী, এ জেড এম নাছিরুদ্দিন, সৈয়দ মঞ্জুর এলাহী, অধ্যাপক নাজমা চৌধুরী ও মেজর জেনারেল (অব.) আব্দুর রহমান খান।
- এই তত্ত্বাবধায়ক সরকার মোট ৮৬ দিন ক্ষমতায় ছিল। এই সরকার ১৯৯৬ সালের ১২ জুন জাতীয় সংসদের নির্বাচনের তারিখ ঘোষণা করেন।
- অবশেষে বিপুল উৎসাহ ও উদ্দীপনা মধ্য দিয়ে ১৯৯৬ সালের ১২ জুন তত্ত্বাবধায়ক সরকারের অধীন প্রথম সপ্তম জাতীয় সংসদ নির্বাচন অনুষ্ঠিত হয়।

উল্লেখ্য,
- ১৯৯০ সালে সেনাশাসক হুসেইন মুহম্মদ এরশাদের পতনের পর জাতীয় নির্বাচন আয়োজন পর্যন্ত দায়িত্ব পালনের জন্য গঠন করা হয়েছিল নির্দলীয় প্রথম অন্তর্বর্তীকালীন সরকার।
- প্রধান বিচারপতি শাহাবুদ্দিন আহমেদের নেতৃত্বে ঐ সরকার গঠিত হয়েছিল।

এছাড়াও,
- ৩০ জুন, ২০১১ সালে পঞ্চদশ সংশোধনীর মাধ্যমে বাংলাদেশের সংবিধান থেকে 'তত্ত্বাবধায়ক সরকার ব্যবস্থা' বাতিল করা হয়।

উৎস: ইতিহাস ২য় পত্র, এইচএসসি প্রোগ্রাম, বাংলাদেশ উন্মুক্ত বিশ্ববিদ্যালয়।

তিস্তা মহাপরিকল্পনা:
- তিস্তা মহাপরিকল্পনা বাস্তবায়নে সহায়তা করবে চীন।

⇒ তিস্তা প্রকল্পের প্রথম পর্যায় বাস্তবায়নে ব্যয় হবে ৭৫ কোটি ডলার। এর মধ্যে চীন থেকে ঋণ চাওয়া হয়েছে ৫৫ কোটি ডলার। বাকিটা করা হবে সরকারি অর্থায়নে।
- চীনের রাস্ট্রদূত জানান, তিস্তা প্রকল্পের বিষয়টিতে অর্থ মন্ত্রণালয়ের অর্থনৈতিক সম্পর্ক বিভাগের (ইআরডি) সঙ্গে তারা কাজ করছেন।
- চীনের বিশেষজ্ঞ দল তিস্তা প্রকল্পের সম্ভাবনা যাচাই শেষে অক্টোবর, ২০২৫-এর মধ্যে তিস্তা মহাপরিকল্পনার ডিজাইন চূড়ান্ত হবে।
- ২০২৬ সালে এ প্রকল্পের কাজ শুরু করে ২০২৯ সালে শেষ করার লক্ষ্যমাত্রা নির্ধারণ করা হয়েছে।
- মহাপরিকল্পনায় তিস্তা নদীর ডান-বাম উভয় তীর ঘেঁষে ২২০ কিলোমিটার উঁচু গাইড বাঁধ, রিভার ড্রাইভ, হোটেল-মোটেল-রেস্তোরাঁ, পর্যটন কেন্দ্র, ১৫০ মেগাওয়াট সৌর বিদ্যুতকেন্দ্র, শিল্প-কারখানা, ইপিজেড, ইকোনমিক জোন, কয়েক লাখ হেক্টর কৃষি জমি উদ্ধার, বনায়ন ইত্যাদি রয়েছে।
- এ প্রকল্প বাস্তবায়ন হলে তিস্তা পাড় হয়ে উঠবে পূর্ব চীনের জিয়াংসু প্রদেশের সুকিয়ান সিটির মতো সুন্দর নগরী।

উৎস: i) প্রথম আলো।
ii) দৈনিক ইনকিলাব।

ড্রাগন ফল উৎপাদন:
- কৃষি সম্প্রসারণ অধিদপ্তরের তথ্য অনুযায়ী, ড্রাগন উৎপাদনের শীর্ষে আছে ঝিনাইদহ জেলা।
- ২০২৪-২৫ অর্থবছরে উৎপাদন হয় ৩২ হাজার ৭৬৮ মেট্রিক টন ড্রাগন।

• উৎপাদনের ২য় স্থানে রয়েছে যশোর। ২০২৪-২৫ অর্থবছরে উৎপাদন হয় ১২ হাজার ৫৫৩ মেট্রিক টন ড্রাগন। আর তৃতীয় শীর্ষ জেলা রাজশাহীতে উৎপাদন হয় ৪ হাজার ৪৭৭ মেট্রিক টন ড্রাগন।

⇒ ড্রাগন ফল মূলত আমেরিকার প্রসিদ্ধ একটি ফল যা বর্তমানে আমাদের দেশেও ব্যাপক জনপ্রিয়তা অর্জন করেছে। বাংলাদেশে সর্বপ্রথম ২০০৭ সালে থাইল্যান্ড, ফ্লোরিডা ও ভিয়েতনাম থেকে এই ফলের বিভিন্ন জাত আনা হয়। ড্রাগন ফলের গাছ এক ধরনের ক্যাকটাস জাতীয় গাছ। এই গাছের কোন পাতা নেই। ড্রাগন ফলের গাছ সাধারনত ১.৫ থেকে ২.৫ মিটার পর্যন্ত লম্বা হয়ে থাকে।

⇒ বর্তমানে বাংলাদেশ কৃষি গবেষণা ইন্সিটিউট (বারি) কতৃক উদ্ভাবিত ড্রগন ফলের নতুন জাতটি হলো বারি ড্রাগন ফল-১ যা দক্ষিণ -পূর্ব এশিয়াতে জনপ্রিয় ফল। এ ফলের আকার বড়, পাকলে খোসার রং লাল হয়ে যায় ,শাঁস গাঢ় গোলাপী রঙের, লাল ও সাদা এবং রসালো প্রকৃতির । ফলের বীজগুলো ছোট ছোট কালো ও নরম । একটি ফলের ওজন ১৫০ গ্রাম থেকে ৬০০ গ্রাম পর্যন্ত হয়ে থাকে।

উৎস: i) প্রথম আলো।
ii) কৃষি বাতায়ন।

OIC:
- ইসলামিক সহযোগিতা সংস্থা OIC.
- OIC এর পূর্ণরূপ The Organisation of Islamic Cooperation.
- ইসরাইল কর্তৃক আল আকসা মসজিদে আগুন ধরিয়ে দেওয়ার প্রেক্ষাপটে OIC গঠিত হয়।
- এটি মুসলিম দেশগুলোর একটি রাজনৈতিক জোট যা রাবাত সম্মেলনের মাধ্যমে গঠিত হয়।
- প্রতিষ্ঠার স্থান: মরক্কো।
- প্রতিষ্ঠিত হয়: ২৫ সেপ্টেম্বর, ১৯৬৯ সালে।
- সদর দপ্তর: জেদ্দা, সৌদি আরব।
- বর্তমান মহাসচিব: হুসাইন ইব্রাহিম তাহা (১২ তম)। (অক্টোবর, ২০২৫)
- মহাসচিবের মেয়াদ: ৫ বছর।
- অফিসিয়াল ভাষা: তিনটি (আরবি, ইংরেজি, ফ্রেঞ্চ)।
- বর্তমান সদস্য: ৫৭টি। (অক্টোবর, ২০২৫)

⇒ দক্ষিণ আমেরিকা অঞ্চলের দুটি দেশ OIC এর সদস্য।
• গায়ানা ও
• সুরিনাম।

- ইউরোপ মহাদেশের আলবেনিয়া OIC এর সদস্য।
- বাংলাদেশ ১৯৭৪ সালের ২২-২৪ ফেব্রুয়ারি পাকিস্তানের লাহোরে অনুষ্ঠিত OIC এর দ্বিতীয় শীর্ষ সম্মেলনে সর্বপ্রথম অংশগ্রহণ করে।

তথ্যসূত্র - OIC অফিসিয়াল ওয়েবসাইট।

কার্টাগেনা প্রটোকল (Cartagena Protocol):
- কার্টাগেনা প্রোটকলের পূর্ণনাম - The Cartagena Protocol on Biosafety to the Convention on Biological Diversity.
- কার্টাগেনা প্রটোকল জৈব-নিরাপত্তা বিষয়ক একটি আন্তর্জাতিক চুক্তি।
- এই চুক্তিটি কলম্বিয়ার কার্টাগেনাতে আলোচিত হয়।
- চুক্তি অনুমোদন - ২৯ জানুয়ারি, ২০০০ সাল।
- চুক্তি কার্যকর - ১১ সেপ্টেম্বর, ২০০৩ সাল।

তথ্যসূত্র - কনভেনশন অন বায়ো-ডাইভার্সিটি (CBD) ওয়েবসাইট।

জাতিসংঘ:
- জাতিসংঘের অর্থনৈতিক ও সামাজিক কমিশন (ECOSOC) এর অধীন ৫টি আঞ্চলিক কমিশন রয়েছে।

⇒ এগুলো হলো:
- এশিয়া ও প্রশান্ত মহাসাগরীয় অর্থনৈতিক ও সামাজিক কমিশন (ESCAP),
- পশ্চিম এশীয় অর্থনৈতিক ও সামাজিক কমিশন (ESCWA),
- ল্যাটিন আমেরিকা ও ক্যারিবীয় অর্থনৈতিক কমিশন (ECLAC),
- ইউরোপিয়ান অর্থনৈতিক কমিশন (ECE),
- আফ্রিকান অর্থনৈতিক কমিশন (ECA).

তথ্যসূত্র - UN ওয়েবসাইট।

ইউরোপীয় ইউনিয়ন (EU):
- বিশ্বের সবচেয়ে বড় অর্থনৈতিক জোট ইউরোপীয় ইউনিয়ন (EU)।
- এর সদর দপ্তর বেলজিয়ামের ব্রাসেলসে অবস্থিত।
- প্রতিষ্ঠাতা সদস্য: ৬টি দেশ।
- বেলজিয়াম, ফ্রান্স, জার্মানি, ইতালি, লুক্সেমবার্গ, নেদারল্যান্ডস।
- বর্তমান সদস্য: ২৭টি দেশ। (অক্টোবর, ২০২৫)
- সর্বশেষ সদস্য: ক্রোয়েশিয়া। (অক্টোবর, ২০২৫)
- সর্বশেষ ত্যাগকারী: ব্রিটেন (৩১ জানুয়ারি, ২০২০)।
- এটি ১৯৯৩ সালের ১ নভেম্বরে মাসট্রিচট চুক্তি স্বাক্ষরের মাধ্যমে প্রতিষ্ঠিত হয়েছিল।
- তখন থেকে এটি বিশ্বের বৃহত্তম ট্রেডিং ব্লকে পরিণত হয়।

তথ্যসূত্র - EU ওয়েবসাইট।

‘অপারেশন রাইজিং লায়ন':
- ইসরায়েল কর্তৃক ইরানে চালানো সামরিক অভিযানটির নাম 'অপারেশন রাইজিং লায়ন'।
- 'রাইজিং লায়ন' নামটি বাইবেলের একটি অনুচ্ছেদে সিংহের প্রতীকী পরাক্রমকে তুলে ধরে, ইসরায়েলের যুদ্ধ প্রস্তুতি এবং আত্মবিশ্বাসের প্রতীক।
- ১৩ জুন ২০২৫-এর ভোরে ইসরায়েলি বিমান বাহিনী ও গোয়েন্দা সংস্থা মোসাদ যৌথভাবে 'অপারেশন রাইজিং লায়ন' পরিচালনা করে।
- ইসরায়েল প্রথমে 'ড্রোন' দ্বারা ইরানের আকাশ প্রতিরক্ষা ব্যবস্থা দুর্বল করা, এরপর প্রধান পারমাণবিক ও সামরিক লক্ষ্যবস্তুতে বিমান হামলা করে।

উল্লেখ্য:
- এই হামলার জবাবে ইরান পাল্টা হামলা চালায়।
- এই হামলার নাম দেয়া হয় 'অপারেশন টু প্রমিজ থ্রি’।
- ইরান পাল্টা জবাবে শতাধিক ক্ষেপণাস্ত্র ও ড্রোন ছুড়ে।

তথ্যসূত্র - পত্রিকার রিপোর্ট।

IUCN:
- বিশ্ব জীববৈচিত্র্য সংরক্ষণবাদী সংস্থা (IUCN)।
- IUCN এর পূর্ণরূপ - International Union for the Conservation of Nature.
- প্রতিষ্ঠিত হয়: ১৯৪৮ সালে।
- সদর দপ্তর: গ্লান্ড, সুইজারল্যান্ড।
- এটি নিয়ে বিশ্বের ১৭০ টির অধিক দেশ কাজ করছে।
- উদ্দেশ্য: বিশ্বব্যাপী প্রাকৃতিক সম্পদ সংরক্ষণ করা।

তথ্যসূত্র - IUCN অফিসিয়াল ওয়েবসাইট।

IMF:
- IMF এর পূর্ণরূপ The International Monetary Fund.
- এটি আন্তর্জাতিক মুদ্রা তহবিল।
- প্রতিষ্ঠিত হয়: ১৯৪৪ সাল।
- সদর দপ্তর: ওয়াশিংটন ডিসি, যুক্তরাষ্ট্র।
- প্রতিষ্ঠাতা সদস্য: ৪৪টি।
- বর্তমান সদস্য: ১৯১টি। (অক্টোবর, ২০২৫)
- সর্বশেষ সদস্য: লিচেনস্টাইন। (অক্টোবর, ২০২৫)
- বর্তমান ব্যবস্থাপনা পরিচালক: ক্রিস্টালিনা জর্জিয়েভা। (অক্টোবর, ২০২৫)
- বাংলাদেশ সদস্যপদ লাভ করে: ১৯৭২ সালে।

তথ্যসূত্র - IMF অফিসিয়াল ওয়েবসাইট।

প্রশ্ন: P হচ্ছে Q এর পিতা কিন্তু Q, P এর ছেলে নয়। তাদের সম্পর্কটা কোন ধরনের?

সমাধান:
যেহেতু, P হচ্ছে Q এর পিতা কিন্তু Q, P এর ছেলে নয় সুতরাং Q হলো মেয়ে এবং P হচ্ছে পিতা।

সুতরাং, তাদের সম্পর্কটা মেয়ে-পিতা।

প্রশ্ন: নিচের চিত্রে কয়টি ত্রিভুজ আছে?

সমাধান:

একটি করে ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 1, 2, 3, 4, 5, 6, 7, 8 = ৮ টি
দুইটি করে ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 12, 34, 56, 78, 67, 58 = ৬ টি
চারটি করে ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 1267, 3456 = ২টি
সবগুলো ফাঁকা ঘর নিয়ে ত্রিভুজ আছে - 12345678 = ১ টি

সুতরাং, মোট ত্রিভুজ আছে = ৮ + ৬ + ২ + ১ = ১৭ টি

প্রশ্ন: একটি পানি ভর্তি বালতির ওজন ১৪ কেজি। বালতিটি অর্ধেক পানি পূর্ণ থাকলে তার ওজন হয় ৮ কেজি। খালি বালতির ওজন কত?

সমাধান:
দেওয়া আছে,
পানি ভর্তি বালতির ওজন = ১৪ কেজি
অর্ধেক পানি ভর্তি বালতির ওজন = ৮ কেজি
​
​অর্ধেক বালতি পানির ওজন = (১৪ - ৮) কেজি = ৬ কেজি
∴ ​পূর্ণ বালতি পানির ওজন = (৬ × ২) কেজি = ১২ কেজি
​
​আবার,
​পূর্ণ বালতি পানির ওজন + খালি বালতির ওজন = ১৪ কেজি
⇒ ​খালি বালতির ওজন = ১৪ - ​পূর্ণ বালতি পানির ওজন
​⇒ ​খালি বালতির ওজন = ১৪ - ১২ = ২ কেজি

প্রশ্ন: যদি ORANGE = SVERKI হয় তবে GRAPES = ?

সমাধান:
​যদি ORANGE = SVERKI হয় তবে GRAPES = KVETIW
​
​ORANGE শব্দটির বর্ণগুলো থেকে 4 ধাপ এগিয়ে পাওয়া যায়,
O(15) + 4 → S(19)
​R(18) + 4 → V(22)
​A(1) + 4 → E(5)
​N(14) + 4 → R(18)
​G(7) + 4 → K(11)
​E(5) + 4 → I(9)

​অনুরূপভাবে,
GRAPES শব্দটির বর্ণগুলো থেকে 4 ধাপ এগিয়ে গেলে KVETIW শব্দটি পাওয়া যায়। অর্থাৎ,
​G(7) + 4 → K(11)
​R(18) +4 → V(24)
​A(1) + 4 → E(5)
​P(16) + 4 → T(20)
​E(5) + 4 → I(9)
​S(19) + 4 → W(23)
​
অর্থাৎ নির্ণেয় শব্দটি হবে KVETIW

প্রশ্ন: যদি 7 + 3 = 410, 3 + 2 = 15, 6 + 5 = 111 হয়, তবে 8 + 4 = ?

সমাধান:
এখানে
7 + 3 = 410 ⇒ 7 - 3 = 4, 7 + 3 = 10
3 + 2 = 15 ⇒ 3 - 2 = 1, 3 + 2 = 5
6 + 5 = 111 ⇒ 6 - 5 = 1, 6 + 5 = 11

একইভাবে,
8 - 4 = 4, 8 + 4 = 12
সুতরাং, 8 + 4 = 412

প্রশ্ন: A দক্ষিণ দিকে মুখ করে ৪ কি. মি. হাঁটার পর বামদিকে ঘুরল এবং ৫ কি. মি. হাঁটল। আবার ডানদিকে ঘুরে ৮ কি. মি. হাঁটল। এখন যাত্রার স্থান থেকে সরাসরি দূরত্ব কত?

সমাধান:
প্রদত্ত তথ্যগুলোকে চিত্রের মাধ্যমে সাজিয়ে পাই,

এখন, উত্তর-দক্ষিণ দিকে- শুরুতে ৪ কি.মি. দক্ষিণ + পরে আরও ৮ কি.মি. দক্ষিণ = মোট ১২ কি.মি. দক্ষিণ
পূর্ব-পশ্চিম দিকে: শুধু পূর্ব দিকে ৫ কি.মি.

∴ সরাসরি দূরত্ব = √(১২^২ + ৫^২) = √(১৪৪ + ২৫)
= √১৬৯
= ১৩ কি.মি.

প্রশ্ন: (A) চিত্রটির আয়নায় প্রতিবিম্ব কেমন হবে?

সমাধান:


সুতরাং, সঠিক উত্তর (2) নং

1.Unit operations are physical processes in chemical engineering where the chemical composition of the substance does not change, only its physical state, size, or energy content changes.
Examples: distillation, evaporation, filtration, crystallization, drying, mixing.
2.Unit processes, in contrast, involve chemical reactions where the chemical composition changes.
3.Biochemical processes → Involve biological reactions, often with chemical changes.
4.Electrochemical processes → Involve electron transfer, leading to chemical changes.

1.Chlor-alkali electrolysis involves the electrolysis of brine (NaCl solution) to produce chlorine, caustic soda (NaOH), and hydrogen.
2.Key points:
It involves electron transfer reactions at electrodes.
The chemical composition changes due to oxidation (Cl⁻ → Cl₂) and reduction (H₂O → H₂ + OH⁻).
3.Hence, it is classified as an electrochemical process.

Other options:
ক) Physical process → Incorrect; chemical composition changes, so not purely physical.
খ) Biochemical process → Incorrect; no biological component is involved.
ঘ) Photochemical process → Incorrect; no light-induced reactions occur.

1.Unit processes are chemical processes where the composition of substances changes through chemical reactions.
Examples include: nitration, sulfonation, oxidation, reduction, chlorination, hydrolysis.
2.They contrast with unit operations, which are purely physical processes (no chemical change), such as distillation, filtration, drying, and evaporation.

Other options:
ক) Operations that handle raw material without energy exchange → Incorrect; unit processes involve chemical reactions, not just handling.
গ) Steps involving only separation techniques → Refers to unit operations, not unit processes.
ঘ) Process that does not include reactors → Incorrect; unit processes generally require reactors for the chemical reactions.

1.Endothermic processes require heat input to proceed.
2.Calcination of limestone (CaCO₃ → CaO + CO₂):
Requires high temperatures (~900°C) to decompose calcium carbonate into calcium oxide (quicklime) and carbon dioxide.
Heat is absorbed from the furnace, making it endothermic.

Other options:
ক) Chlorination → Often exothermic, releases heat.
খ) Sulfonation → Exothermic reaction.
ঘ) Nitration of Benzene → Exothermic reaction, releases heat.

Unit operations involve physical changes of materials without altering chemical composition.

Examples: distillation, filtration, evaporation, drying, crystallization, mixing.
Unit processes, in contrast, involve chemical changes where substances are transformed chemically.
Modern chemical plants may use both batch and continuous processes, so option ক is incorrect.
Unit operations and unit processes do not overlap completely; one is physical, the other chemical, so option খ is wrong.
Heat transfer may be required in unit operations (e.g., distillation), so option ঘ is incorrect.

1.Petrochemical plants require large amounts of feedstock (crude oil, natural gas, naphtha, etc.) and energy for processing.
2.Selecting a site near raw material sources, pipelines, ports, and reliable power supply:
Reduces transportation costs
Improves operational efficiency
Minimizes supply chain risks

Other optionst:
খ) Local availability of furniture suppliers → Not critical for plant operation.
গ) Distance from tourist attractions → Not a technical factor.
ঘ) Building color codes → Cosmetic, not a major factor.

1.Topography refers to the natural features of the land, such as slopes, elevations, and terrain.
2.It affects:
Drainage: Sloped land aids runoff, reducing flooding risk.
Construction costs: Uneven terrain may require land leveling, retaining walls, or extensive earthwork, increasing costs.
3.Proper site selection ensures efficient plant layout and reduced civil engineering challenges.

Other options:
ক) Raw material purity → Depends on the source, not topography.
গ) Labor skill levels → Related to local workforce, not terrain.
ঘ) Catalyst efficiency → Dependent on process conditions, not site topography.

In chemical industry site selection, logistics cost mainly depends on how easily raw materials can be brought in and finished products can be transported to markets. Therefore, being close to markets and having good transportation facilities (roads, railways, ports, etc.) reduces logistics cost significantly.

The other options (soil bearing capacity, number of local schools, wind speed data) may influence other aspects of site selection, but they are not directly related to logistics cost.

Seismic activity data is important in site selection because areas prone to earthquakes require special design considerations, stronger structures, and safety measures to protect both equipment and personnel. It does not directly affect operating cost, chemical reactions, or worker productivity, but it plays a critical role in ensuring the safety and long-term reliability of the plant.

Environmental Impact Assessment (EIA) is carried out during site selection to evaluate how the proposed plant may affect air, water, soil, biodiversity, and surrounding communities. Its main goal is to prevent or minimize ecological damage, reduce pollution, and ensure compliance with environmental regulations and laws.

It has nothing to do with product yield, depreciation, or plant aesthetics.

Fertilizer plants (e.g., urea, ammonia, phosphate fertilizers) are designed to operate continuously because:

Demand is large and consistent worldwide.
Production needs to be high-volume to be economically viable.
Processes like ammonia synthesis and urea production run 24/7 to maintain efficiency.
Other options such as batch, semi-batch, or discontinuous are more typical for pharmaceuticals, fine chemicals, or specialty products, not fertilizers.

Energy integration in modern chemical plants (e.g., heat exchangers, pinch analysis, cogeneration) is used to:

1.Recover and reuse energy within the plant (e.g., using hot process streams to preheat cold ones).
2.Reduce fuel and utility consumption, lowering operating cost.
3.Improve sustainability by minimizing greenhouse gas emissions and reducing dependency on external energy sources.
It does not reduce yield, increase capital unnecessarily, or increase reliance on fossil fuels.

Chemical technology strengthens industrial competitiveness by:

1.Allowing scale-up from lab to pilot to full industrial production.
2.Optimizing processes for higher efficiency, lower energy use, and reduced waste.
3.Introducing automation and advanced control systems to improve productivity, safety, and consistency.
It is not about simply adding more manual labor, blindly replacing raw materials, or skipping quality control — those would actually harm competitiveness.

Advanced chemical technology is the backbone of green manufacturing because it:

1.Focuses on waste prevention at the source rather than only treating pollutants at the end.
2.Promotes process intensification (making processes more efficient, compact, and less resource-intensive).
3.Facilitates energy efficiency, renewable integration, and circular use of resources.
The other options (more raw material consumption, only end-of-pipe treatment, avoiding renewables) go against the principles of green chemistry and sustainable manufacturing.

Process intensification aims to make chemical processes more efficient, compact, and sustainable. Microreactors are a prime example because they:
1.Provide very high surface area-to-volume ratio, enhancing heat and mass transfer.
2.Allow safer operation at high pressures/temperatures in small volumes.
3.Enable faster reactions, higher selectivity, and reduced waste.

Other options:
Larger reactors → increase scale, not intensification.
Less accurate control → reduces efficiency and safety.
Eliminating safety systems → unsafe and against modern chemical engineering principles.

In a steady, incompressible, irrotational flow of an ideal fluid:

1.Irrotational means vorticity = 0 everywhere.
2.Pressure is not uniform (it varies with velocity and height, see Bernoulli’s principle).
3.Velocity is not necessarily zero at all boundaries (depends on boundary condition, e.g., slip condition for ideal fluids).
4.Shear stress in an ideal fluid is always zero (since viscosity = 0), so it cannot be maximum at stagnation points.

The Reynolds number is given by:

Re=ρ V D/μ

Where,
ρ = fluid density
V= average velocity
D= pipe diameter
μ = dynamic viscosity
Here, Re is directly proportional to the diameter.
1. Initial Re1=5×10⁴
2. If D is doubled (2D) while V,ρ,μ remain the same:
Re2=ρ V (2D)/μ=2×Re1=1×10⁵
So the Reynolds number doubles.

The Reynolds number (Re) is defined as:
Re=Inertial forces/Viscous forces=ρVL/μ
​Where:
ρ = fluid density
V= characteristic velocity
L = characteristic length
μ = dynamic viscosity
A high Re indicates inertial forces dominate (turbulent flow), and a low Re indicates viscous forces dominate (laminar flow).

Other options:
Froude number → ratio of inertial to gravitational forces (important in open channel flow).
Weber number → ratio of inertial to surface tension forces (important in droplet formation).
Mach number → ratio of flow velocity to speed of sound (compressibility effects).

Bernoulli’s equation is derived for ideal, incompressible, inviscid (non-viscous), steady flow along a streamline. Its main limitation in practical engineering is that:

1.Viscous effects in real fluids cause pressure drops due to friction, which Bernoulli’s equation cannot capture.
2.It does not inherently include energy losses from pumps, valves, bends, or turbulence.

Other options :
It can be applied to compressible fluids under certain approximations (e.g., low Mach number).
It does not assume constant pressure; pressure varies along the streamline.
Density variations are only an issue for compressible flows; Bernoulli can be adapted with assumptions.

A rotameter is a variable-area flow meter consisting of:

1.A tapered vertical tube
2.A float that rises and falls depending on the flow rate
3.As flow increases, the float moves higher in the tube, increasing the cross-sectional area for fluid to pass, until the upward drag force equals the float’s weight.
4.The flow rate can be read directly from a calibrated scale.

Other options:
Venturi meter → uses pressure difference across a constriction.
Orifice meter → uses a plate with a hole to create a pressure drop.
Pitot tube → measures fluid velocity based on stagnation pressure.

1.In cathodic protection using sacrificial anodes, a more active (more negative electrode potential) metal is connected to the metal to be protected.
2.The sacrificial anode corrodes preferentially, protecting the main metal (making it the cathode).
3.Common sacrificial anodes: zinc, magnesium, aluminum for steel structures.

Other options :
Higher electrode potential → the protected metal would corrode instead.
Same potential → no current flows, so no protection.
Corrosion resistance alone does not guarantee effective protection; electrochemical potential difference is the key.

1.A Pourbaix diagram (potential–pH diagram) shows the thermodynamic stability of a metal in aqueous environments.
2.The “immune” region corresponds to conditions (pH and potential) where the metal is thermodynamically stable, i.e., it does not oxidize or corrode.

Other options:
Active corrosion: metal dissolves to form ions.
Passivation: metal forms a protective insoluble oxide layer.

1.Organic inhibitors (like amines, thiols, phosphates) work by adsorbing onto the metal surface and forming an insoluble protective layer.
2.This layer blocks corrosive species (like H⁺, Cl⁻) from reaching the metal, reducing corrosion rate.

Other options:
Anodic protection → maintains the metal in a passive state by controlling potential.
Cathodic protection → makes the metal the cathode to prevent oxidation.
Alloying with nickel → improves corrosion resistance but does not form a surface complex.

1.The Huey test is a standard chemical test to detect intergranular corrosion (IGC) in stainless steels.
2.It involves immersing a sample in boiling nitric acid; susceptible areas at grain boundaries preferentially corrode, revealing the degree of sensitization.

Other options:
Salt spray test → general corrosion resistance, not specific to IGC.
Potentiodynamic polarization → electrochemical method for general corrosion or pitting studies.
Electrochemical impedance spectroscopy (EIS) → studies corrosion kinetics and protective coatings, not specific for IGC.

In electrochemical corrosion, the cathodic reaction often involves oxygen reduction:
O2+4e−+2H₂O→4OH
Increasing oxygen concentration in the electrolyte:
Enhances the rate of the cathodic reaction.
Leads to an increase in the overall corrosion rate of the metal.

Other options:
Decreasing cathodic rate → happens when oxygen is limited.
Corrosion does not stop automatically; protective layers form only under specific conditions (passivation).
Saying it has no effect ignores the direct role of oxygen in the cathodic reaction.

In the lower part of the blast furnace, carbon monoxide (CO) acts as a reducing agent:
FeO+CO→Fe+CO₂
This reaction typically occurs in the temperature range of 400–700 °C, converting iron oxide to molten iron.

Other options:
CO does not act as a carburizing agent (that’s mainly done by molten carbon/soot).
CO does not oxidize silicon; Si is removed in slag formation by reactions with CaO.
CO does not react with CaO to form CaCO₃; that is not part of the blast furnace chemistry.

In the Bessemer process, phosphorus in pig iron is oxidized to P₂O₅:
4P+5O₂→2P₂O₅
​Basic-lined converters (lined with CaO) react with P₂O₅ to form calcium phosphate (Ca₃(PO₄)₂) in the slag:
P₂O₅+3CaO→Ca₃(PO₄)₂
​This removes phosphorus efficiently, whereas acid-lined converters do not form stable phosphate compounds, making phosphorus removal poor.

Other options :
The lining is not an oxidizing agent.
It does not significantly lower the temperature.
Phosphorus affinity for silicon is irrelevant here.

In the iron–carbon phase diagram, at 727 °C (the eutectoid temperature) and 0.8 wt% C:

γ-Fe (austenite)→α-Fe (ferrite)+Fe₃C (cementite)

This eutectoid transformation produces pearlite, a lamellar mixture of ferrite and cementite.

Other options :
Austenite → Ferrite alone occurs at lower carbon content, not at eutectoid composition.
Ferrite → Austenite happens during heating above 727 °C.
Cementite → Austenite is not a direct transformation at this temperature.

1.Manganese is added to steel primarily to counteract the harmful effects of sulfur, which causes hot-shortness (brittleness when hot) by forming FeS.
2.Manganese reacts with sulfur to form MnS, which has a higher melting point and does not cause brittleness, improving hot workability.

Other options :
It does not significantly lower melting point.
It does not directly increase carbon solubility.
Oxidation resistance is mainly enhanced by chromium, not manganese.

In a blast furnace, the reduction of iron oxides occurs in a stepwise manner from top to bottom as the temperature increases:

Hematite → Magnetite:
3Fe₂O₃+CO→2Fe₃O₄+CO₂
Magnetite → Wüstite:
Fe₃O₄+CO→3FeO+CO_{2
Wüstite → Iron:
Fe + CO_2FeO+CO→Fe+CO2​}
The lower part is hotter, where FeO reduces to molten iron.

Other sequences are incorrect because they do not follow the actual thermal reduction order.

1.The minimum reflux ratio (Rₘᵢₙ) in a binary distillation column is the lowest reflux ratio at which the desired separation is theoretically possible.
2.At Rₘᵢₙ, the column would require an infinite number of theoretical stages to achieve the separation.
3.Practically, distillation is operated at a higher reflux ratio (typically 1.2–1.5 × Rₘᵢₙ) to reduce the number of stages and achieve feasible column height.

Other options:
Maximum distillate rate → occurs at total reflux.
100% separation → idealization, not directly linked to Rₘᵢₙ.
Zero reboiler duty → theoretical concept at total reflux, not minimum reflux.

In a plate (trayed) distillation column, the column diameter is primarily determined by the volumetric vapor flow rate:

1.If the vapor velocity is too high, flooding occurs (liquid is carried upward by vapor).
2.If the vapor velocity is too low, capacity is underutilized and column is oversized.
3.The number of stages, feed composition, and plate efficiency affect column height and number of trays, but not diameter directly.

Bubble-cap trays:
Can handle wide variations in vapor and liquid flow without flooding or weeping.
Are more complex and expensive due to caps, risers, and assembly.
Sieve trays:
Simpler, cheaper, and lighter.
Have a narrower operating range and may suffer from weeping at low vapor rates.

Other options:
Sieve trays do not inherently have higher pressure drop.
Bubble-cap trays are not simpler or cheaper.
Sieve trays are not ideal for low vapor rates; bubble-caps perform better there.

1.Weeping occurs in sieve trays when the upward vapor velocity is insufficient to support the liquid on the tray holes.
2.As a result, liquid leaks through the perforations instead of being properly vaporized, reducing tray efficiency.

Other options :
Vapor velocity too high → causes flooding, not weeping.
Slow downcomer flow → may cause liquid backup, but not weeping.
Tray spacing too large → affects column height and vapor-liquid contact but is not the primary cause of weeping.

In the McCabe–Thiele method for binary distillation:

The q-line represents the thermal condition of the feed:

q=fraction of liquid in the feedq = ext{fraction of liquid in the feed}q=fraction of liquid in the feed
Slope of q-line:

m=q/q​−1​
It helps determine the intersection point between rectifying and stripping operating lines.

Other options:
Slope of operating lines → separate lines for rectifying and stripping sections, not the q-line.
Equilibrium curve → represents vapor-liquid equilibrium, different from q-line.

1.Superheating the refrigerant vapor at the evaporator exit ensures that only vapor enters the compressor, preventing damage from liquid droplets (liquid slugging).
2.Slightly reduces the refrigeration effect because the evaporator absorbs a small extra amount of heat to superheat the vapor without contributing to phase change cooling.

Other options:
Does not significantly reduce mass flow rate or increase COP directly.
Does not increase condenser pressure; that is determined by the condenser temperature and load.
Any impact on refrigeration effect is slight, not major increase or reduction in compressor work.

In an ammonia–water absorption refrigeration system:

1.The solution pump moves the weak ammonia solution from the absorber (low pressure) to the generator (high pressure).
2.This raises the pressure of the solution above the condenser pressure, enabling the ammonia vapor to boil off in the generator and continue the refrigeration cycle.

Other options :
Maintaining ammonia flow through the evaporator → happens due to vapor pressure, not the pump.
Increasing evaporator pressure → not the pump’s function.
Driving the rectifier → unrelated to the solution pump.

In a vapor-compression refrigeration system, throttling (expansion) losses occur in the expansion device where the refrigerant pressure drops.
To minimize these losses:
1.The refrigerant should have high latent heat of vaporization, so more cooling is achieved per unit mass.
2.Low viscosity ensures easy flow through the expansion device and reduces pressure drops in pipes.

Other options :
High specific heat → affects sensible heat, not phase-change cooling.
High boiling point → could reduce evaporator effectiveness.
Low critical temperature → limits condensation temperature, not directly throttling loss.

1.A combined compression–absorption cascade system uses:
A vapor-compression cycle for the high-temperature stage
An absorption cycle for the low-temperature stage
2.This combination allows the system to achieve very low evaporator temperatures (e.g., −70 to −100 °C) more efficiently than a single cycle alone.

Other options :
It does not eliminate the need for a condenser; each cycle still has a condenser.
Reducing generator temperature → not the primary advantage; the absorption cycle still requires sufficient heat input.
Reducing compressor discharge pressure → secondary effect, not the main purpose.

R-717 (ammonia) is widely used in industrial refrigeration because:
It has excellent thermodynamic properties, giving high coefficient of performance (COP).
It has zero ozone depletion potential (ODP) and no global warming potential (GWP).

Other options:
Ammonia is toxic and flammable, so safety measures are required.
It is not compatible with all metals (e.g., copper) without care.
It does not necessarily operate at very low pressures; pressures depend on system design.

1.Photochemical smog forms when NOₓ and VOCs react under sunlight (UV radiation).
2.These reactions produce ground-level ozone (O₃) and other secondary pollutants like peroxyacetyl nitrate (PAN).
3.Key characteristics:
Typical in sunny, urban areas with vehicle emissions.
Involves oxidation reactions driven by sunlight, unlike classical sulfurous smog.

Other options:
(ক) Describes sulfurous smog (London-type), not photochemical smog.
(গ) and (ঘ) ignore the role of sunlight and NOₓ/VOCs chemistry.

1.Heavy metals like cadmium, chromium, and lead are:
Non-biodegradable – they do not break down naturally.
Persistent in the environment and accumulate in organisms through the food chain (bioaccumulation and biomagnification).
2.This leads to toxicity in aquatic life, humans, and wildlife, even at low concentrations.

Other options :
They do not evaporate significantly; they mainly contaminate water and soil.
They do not neutralize acids or enhance oxygen content; in fact, they can reduce water quality.

Global warming mitigation requires reducing greenhouse gas (GHG) emissions and enhancing carbon sinks. Key strategies include:

Reducing deforestation → preserves forests that absorb CO₂.
Promoting renewable energy → replaces fossil fuels, lowering CO₂ emissions.
Limiting methane from livestock → tackles a potent GHG.

Other options:
Increasing urbanization/industrial expansion without emission controls → increases emissions.
Releasing CFCs/halons → depletes ozone and is harmful; does not mitigate global warming.
Coal-based generation, even with fly ash capture → still emits large amounts of CO₂.

Ozone depletion over Antarctica (the ozone hole) occurs mainly due to:
1.CFCs and halons released by human activities.
2.These compounds release Cl and Br radicals in the stratosphere.
3.In the cold Antarctic winter, these radicals catalyze the destruction of ozone (O₃ → O₂).

Other options:
Methane, CO₂, NO₂ → contribute to global warming, not the Antarctic ozone hole.
Solar radiation alone → necessary for photochemical reactions but requires CFCs/halons to cause depletion.

1.Chemical Oxygen Demand (COD) measures the total amount of oxidizable organic matter in wastewater.
2.Biological treatment (aerobic or anaerobic) is most effective because:
Microorganisms metabolize organic compounds, significantly reducing COD.
Aerobic treatment (activated sludge, trickling filters) works fast for soluble organics.
Anaerobic treatment is effective for high-strength, organic-rich wastewater and produces biogas.

Other options:
Primary sedimentation → removes only settleable solids, not dissolved organics.
Simple dilution → does not reduce COD, only lowers concentration temporarily.
Open landfilling → does not treat wastewater; may cause secondary pollution.

Ultrafiltration (UF) membranes:
Have pore sizes in the range of 1–100 nm.
Can remove suspended solids, colloids, macromolecules, and most bacteria and some viruses.
Do not remove dissolved salts or small ions; for that, nanofiltration or reverse osmosis is needed.

Other options :
UF does not primarily remove dissolved salts.
It does not rely on electrical potential (that is electrodialysis).
UF removes both particulates and organics, not only organics.

Activated carbon is widely used in water treatment because of its high surface area and porous structure, which makes it very effective at:
Adsorbing dissolved organic contaminants
Removing undesirable tastes and odors
Dechlorination of water

Other options :
Suspended solids → removed by sedimentation or filtration, not activated carbon.
Microbial pathogens → require disinfection (chlorination, UV, ozone).
Hardness salts → removed by ion exchange or precipitation, not adsorption on carbon.

1.Dhaka WASA Mirpur Plant draws its raw water mainly from the Buriganga River.
2.The plant uses conventional water treatment processes:
Coagulation and flocculation – to aggregate suspended particles
Sedimentation – to settle out flocs
Filtration – to remove remaining particulates
Chlorination – to disinfect and ensure safe drinking water

Other options:
Chittagong Karnaphuli Plant uses the Halda River, not Buriganga.
Khulna Municipal Water Plant uses surface water from local rivers, not specifically Buriganga.
Rajshahi Deep Tube Well Plant relies on groundwater, not surface water.

Electrodialysis (ED) is an electrochemical process where ions are transported through selective ion-exchange membranes under an applied electric potential.
Factors affecting ion transport rate:
Applied voltage – higher voltage increases ion migration.
Ion concentration gradient – steeper gradients enhance transport.
Temperature – higher temperatures increase ion mobility and conductivity.

Other options :
Pressure difference → relevant for pressure-driven processes (like RO), not ED.
pH alone → affects speciation but does not drive ion transport without voltage.
Suspended solids → may foul membranes, but do not directly drive ion transport.

Biodegradability index (BI) is defined as:
BI=BOD/COD
​For the given wastewater:
BI=480600=0.8

Other options:
BI > 0.6 – 0.8 → highly biodegradable; suitable for biological treatment.
BI 0.3–0.6 → moderately biodegradable; may require longer retention or enhanced treatment.
BI < 0.3 → poorly biodegradable; may require chemical or advanced treatment.

The Frasch process is used for extracting elemental sulfur from underground deposits.
Key steps:
1. Superheated water (~165–170 °C) is injected into the sulfur deposit to melt the sulfur.
2. Compressed air may be used to help lift the molten sulfur to the surface.
3. The molten sulfur is pumped out for collection.

Other options:
Direct combustion → destroys sulfur, not extraction.
Sublimation → used for purification, not typical large-scale extraction.
Organic solvents → not used in the Frasch process.

During sulfide ore roasting, sulfur dioxide (SO₂) is emitted:
4FeS₂+11O₂→2Fe₂O₃+8SO₂
If SO₂ is released into the atmosphere and deposits on soil, it can form sulfuric acid via reaction with water:
SO₂+H₂O→H₂SO₃
2SO₂​+O_2​+2H_2​O→2H_2​SO_4​
​This acid rain or local deposition leads to soil acidification, damaging vegetation and ecosystems.

Other options :
Hydrogen gas → flammable but does not acidify soil.
Ozone → reactive gas, short-lived; minor effect on soil.
Elemental sulfur residues → inert unless oxidized over time, less immediate impact than SO₂ emissions.

Oleum (H₂S₂O₇) is formed when sulfur trioxide (SO₃) is dissolved in concentrated sulfuric acid:
H₂SO₄+SO₃→H₂S₂O₇
​Why oleum is used:
It allows the production, storage, and transport of very concentrated sulfuric acid (>98%) safely.
Later, it can be diluted with water to the desired concentration without handling highly fuming concentrated acid directly.

Other options :
Reducing SO₂ emissions → managed by gas absorption towers, not by forming oleum.
Acting as a catalyst → the contact process uses V₂O₅, not oleum.
Increasing hydrogen production → unrelated to oleum.

The Claus process is used to treat hydrogen sulfide (H₂S) from natural gas and refinery streams.
Key advantage:
Instead of directly burning H₂S to SO₂, which releases harmful sulfur dioxide into the atmosphere, the Claus process converts a large portion of H₂S into elemental sulfur (S₈), which can be recovered and sold.

Other options:
Complete elimination of SO₂ → not entirely; some residual SO₂ is produced.
Production of sulfuric acid → that occurs in the contact process, not Claus process.
Reduction of NOₓ → not a primary feature of Claus process.

Acid rain is primarily caused by SO₂ and NOₓ emissions, which react with water to form sulfuric and nitric acids:
SO₂+H₂O→H₂SO₃

- ​Major anthropogenic source:
Burning fossil fuels (coal, oil, and petroleum products) containing sulfur impurities produces large quantities of SO₂, leading to acid rain.

Other options :
Volcanic sulfur → natural, episodic, not the main anthropogenic source.
Hydrogen sulfide from natural gas → generally oxidized before release; minor contribution.
Sulfate salts in seawater → natural, not anthropogenic.

1.In urea production, ammonia and CO₂ first react to form ammonium carbamate, which then dehydrates to give urea.
2.Not all ammonia and CO₂ are converted in a single pass. To minimize raw material loss and reduce energy consumption, unreacted gases are recovered, decomposed, and recycled back into the reactor.
3.This recycling step is the main energy-saving measure in modern urea plants (e.g., Stamicarbon, Snamprogetti processes).

Other options:
(ক) Low-pressure ammonia synthesis is about ammonia production, not urea.
(গ) Increasing water content increases evaporation load → more energy.
(ঘ) Rapid cooling is part of crystallization, not a major energy-saving factor.

1.Ammonia plants in Bangladesh (such as those under BCIC – Bangladesh Chemical Industries Corporation) are based on natural gas as feedstock.
2.They do not use sulfur-containing feedstock, so SO₂ emissions (ঘ) are not a major issue.
3.NOₓ emissions (ক) are relatively minor compared to power plants and vehicles.
4.Fluoride contamination (খ) is not linked to ammonia production processes.
5.The main environmental concern is ammonia leakage from storage tanks, pipelines, compressors, and urea solution handling.
Ammonia in air is toxic and corrosive.
In water, it increases BOD/COD and harms aquatic ecosystems.

1.Triple Superphosphate (TSP) is produced by reacting phosphate rock with phosphoric acid.
2.The granule size and uniformity in the granulation drum depend mainly on:
Reaction temperature → affects slurry viscosity and crystallization rate.
Acid-to-rock ratio → determines the degree of reaction and slurry consistency.
3.Proper control of these ensures good granulation, minimal dust, and uniform particle size.

Other options:
(খ) Ammonia feed rate from urea plant → unrelated, since ammonia isn’t used in TSP production (it’s used in DAP, MAP, urea).
(গ) Hydrogen content in natural gas → relevant for ammonia plants, not TSP.
(ঘ) Pressure in ammonia synthesis loop → again, ammonia plant–related, not TSP.

1.In Bangladesh, ammonia plants produce NH₃ mainly from natural gas.
2.During hydrogen production (steam reforming of methane), a large amount of CO₂ is generated as by-product.
3.Instead of venting this CO₂ to the atmosphere, it is captured and fed to the urea plant, where it reacts with ammonia to form urea (via ammonium carbamate intermediate).
4.This integration achieves two goals:
Energy efficiency – heat and material integration between plants.
Environmental benefit – reduces CO₂ emissions by utilizing it as feedstock.

Other options:
(ক) Phosphate rock consumption → relates to TSP/DAP, not ammonia–urea.
(খ) Ammonia volatilization in TSP → ammonia isn’t used in TSP.
(গ) Neutralizing acidic effluents → usually lime or neutralization units are used, not ammonia–urea integration.

1.In Triple Superphosphate (TSP) production, phosphate rock is digested with phosphoric acid.
2.This produces slurry and acidic effluents (mother liquor) containing unreacted H₃PO₄ and soluble phosphates.
3.Discharging this directly → causes acidic wastewater pollution.
Technological solution:
Recycle mother liquor back into the process → reduces fresh acid demand.
Neutralize residual acidity with lime (CaO/Ca(OH)₂) before discharge → ensures effluent meets environmental standards.

Other options:
(ক) Low-grade phosphate rock → increases impurities, worsens waste quality.
(খ) Increasing reaction temperature → won’t remove acid, just affects slurry properties.
(ঘ) Reducing particle size → improves reactivity but does not reduce acidity without control.

In sugarcane processing:

Juice extraction → by milling or diffusion.
Clarification → lime treatment, carbonation/sulphitation to remove impurities.
Concentration → clarified juice is evaporated under vacuum evaporation to produce thick syrup.
Crystallization → under controlled cooling, sucrose crystallizes out from the syrup.
Centrifugation → separates raw sugar crystals from the mother liquor (molasses).

Other options:
(ক) Carbonatation and clarification → removes non-sugars, but doesn’t separate sugar from molasses.
(খ) Diffusion and filtration → for juice extraction, not final sugar separation.
(গ) Lime treatment and carbonation → juice purification step only.

1.Bagasse = the fibrous residue left after extracting juice from sugarcane.
2.In Bangladesh sugar mills, bagasse is widely used as a renewable fuel in boilers to generate:
Steam → used for evaporation and crystallization.
Electricity (cogeneration) → some mills even supply excess power to the grid.
3.This makes bagasse the primary renewable energy source in the sugar industry.

Other options:
(ক) Molasses → mainly used for alcohol/ethanol production and cattle feed, not energy in mills.
(গ) Press mud → used as fertilizer, not for energy.
(ঘ) Filter cake' → same as press mud, agricultural use.

1.In Bangladesh, the sugar industry is struggling mainly due to:
Old and inefficient mills under BCIC → low recovery rate (only ~7–8% sugar from cane, compared to >10–12% in modern mills).
Seasonal supply of sugarcane → cane is available only for a few months, leaving mills idle the rest of the year.
2.Farmers also prefer other cash crops (rice, jute) over sugarcane due to low profitability, making raw material shortage worse.

Other options:
(খ) Overproduction & export surplus → opposite situation; Bangladesh is a net sugar importer.
(গ) Excessive sugar beet cultivation → sugar beet is not commercially cultivated in Bangladesh.
(ঘ) Lack of byproduct utilization → true to some extent, but not the major challenge (bagasse and molasses are partially used).

1.Coal classification is based on rank, which reflects the degree of coalification (how far the coal has progressed from peat to anthracite).
2.The two key indicators of rank are:
Fixed carbon content → increases with rank.
Calorific value (heating value) → also increases as coal matures.
Classification by rank:
Lignite → lowest rank, high moisture, low fixed carbon, low calorific value.Sub-bituminous → higher heating value than lignite, moderate fixed carbon.
Bituminous → widely used in industry, high fixed carbon, higher calorific value.
Anthracite → highest rank, very high fixed carbon (>85%), highest calorific value, burns cleanest.

Other options:
(ক) Moisture content → decreases with rank, but not the main classification basis.
(গ) Sulfur content → environmental concern, varies within ranks.
(ঘ) Ash content → depends on mineral matter, not rank-determining.

1.During coke production (carbonization of coal in coke ovens), large lumps of coke are produced.
2.The fine particles (usually <10 mm) generated during handling and screening are called coke breeze.
3.Coke breeze has limited use in blast furnaces (too fine for good permeability) but is valuable as:
Fuel in sintering of iron ore.
Fuel in foundries and some industrial boilers.
Reductant in small-scale metallurgical operations.

Other options:
(খ) Residual coal after gasification → not called coke breeze.
(গ) Coal slurry in power plants → unrelated, that’s just coal-water mixture.
(ঘ) Molasses-like byproduct → refers to coal tar, not coke breeze.

1.Coal combustion (in power plants, boilers, or industrial furnaces) produces fly ash and fine particulates.
2.Electrostatic precipitators (ESP) are devices that:
Charge the particles electrically.
Collect them on oppositely charged plates.
Remove >99% of particulates before flue gas is released.
3.This is the most effective method to control particulate emissions from coal-fired units.

Other options:
(খ) Lime addition during gasification → controls SO₂, not particulates.
(গ) Carbonization at high temperature → related to coke production, not particulate control.
(ঘ) Natural ventilation of coal mines → helps worker safety underground, not flue gas particulate control.

1.Bangladeshi coal (mainly from the Barapukuria, Phulbari, Dighipara fields) is generally lignite to sub-bituminous in rank.
2.Key characteristics:
High volatile matter → burns easily and produces good flame, suitable for steam generation in thermal power plants.
Moderate ash content → manageable in boilers.
3.Not suitable for metallurgical (coke) use because:
Low fixed carbon → poor coking properties.
High moisture → reduces heating value and coke strength.

Other options:
(ক) Extremely low moisture → not true; Bangladeshi coal has moderate to high moisture.
(খ) Very high fixed carbon → needed for metallurgical coke, not characteristic of local coal.
(গ) Low sulfur content → environmentally favorable, but doesn’t determine suitability for power vs coke.

1.In a refinery, after atmospheric distillation, the heavier fractions (residues) are sent to a vacuum distillation column.
2.Purpose of vacuum distillation:
Reduce pressure → lowers the boiling point of heavy fractions, preventing thermal cracking.
Separate heavy products → vacuum gas oil, lubricating oil base stocks, waxes, asphalt.
3.This allows high-quality lubricating oils to be obtained without degrading them.

Other options:
(ক) LPG and naphtha → separated in atmospheric distillation, not vacuum.
(গ) Sulfur removal → done via hydrodesulfurization (HDS) units.
(ঘ) Improve octane → done in reforming, isomerization, or blending, not distillation.

1.Thermal cracking involves heating heavy hydrocarbons (like residual oils or heavy gas oils) to high temperatures (450–750°C) without catalysts.
2.The C–C bonds break randomly, producing:
Light alkenes (olefins) → ethylene, propylene, butenes.
Some lighter paraffins → methane, ethane, propane.
3.These light olefins are key feedstocks for petrochemical industries (polyethylene, polypropylene, etc.).

Other options:
(ক) High-octane gasoline and aromatics → mainly produced by catalytic cracking (FCC).
(খ) Low-sulfur diesel → depends on feedstock and desulfurization, not thermal cracking.
(গ) High-quality lubricants → obtained from vacuum distillation or solvent extraction, not cracking.

1.Catalytic reforming is a refinery process to improve gasoline octane.
2.The key reactions include:
Dehydrogenation of naphthenes → produces aromatics.
Isomerization of straight-chain alkanes (paraffins) → forms branched alkanes, which have higher octane numbers.
3.Other minor reactions: cyclization and hydrocracking, but octane improvement mainly comes from isomerization.

Other options:
(খ) Cracking → produces lighter fractions (LPG), not primarily for octane.
(গ) Removal of sulfur → done in hydrodesulfurization, not part of octane boosting.
(ঘ) Polymerization → not relevant in reforming; used in olefin plants.

1.Hydrocracking is a catalytic process that breaks heavy hydrocarbons into lighter, more valuable products.
2.Key features:
Requires a bifunctional catalyst (acidic + metal sites).
High pressure hydrogen is used to:
Saturate olefins formed during cracking.
Prevent coke formation.
Exothermic because hydrogenation reactions release heat.
3.Products include: LPG, naphtha, kerosene, diesel, depending on conditions and feed.

Other options:
(ক) Requires catalyst → true, so (ক) is incorrect.
(খ) Only LPG and gasoline → incorrect; can produce middle distillates too.
(ঘ) Exclusively for lubricants → incorrect; hydrocracking is for fuels, not lubricants.

1.Eastern Refinery Limited (ERL) is the only major crude oil refinery in Bangladesh, located in Chittagong.
2,Key facts:
Refining capacity: ~ 1.5 million tons/year (≈30,000 barrels/day).
Produces petrol, diesel, kerosene, furnace oil, jet fuel, and LPG.

Other options:
(খ) Barapukuria → coal mine, not a refinery.
(গ) Sylhet Refinery → no such commercial refinery.
(ঘ) Meghna Refinery → proposed/fictional, does not exist at 7 million tons/year.

1.Nanostructured glass in photonics is engineered at the nanoscale to control optical properties.
2.Key mechanism:
Uniformly dispersed nanocrystals (like silica, titania, or rare-earth oxides) within the glass matrix:
Reduce light scattering and attenuation.
Enhance mechanical strength due to nanocrystal reinforcement.
Allow precise control of refractive index.

Other options:
(খ) Porosity gradients → mainly used in some glasses for insulation or toughness, not typical in photonics.
(গ) Thermal tempering → improves bulk strength but doesn’t explain nanoscale optical control.
(ঘ) Large metallic particles → increase scattering, undesirable for low-loss photonics.

1.Glass-ceramics like Pyroceram are produced by controlled crystallization of certain glasses.
2.Manufacturing steps:
Form a glass by melting and cooling the raw materials.
Add nucleating agents (e.g., TiO₂, ZrO₂) → promote uniform formation of crystal nuclei.
Heat-treat the glass at specific temperatures → controlled growth of nanocrystals within the matrix.
Result: materials with excellent thermal stability, mechanical strength, and low thermal expansion.

Other options:
(ক) Rapid cooling + reheating → part of glass annealing, but nucleating agents are needed for uniform crystallization.
(খ) Porosity → not used for controlled nucleation.
(ঘ) Quenching in water → creates stresses, not controlled crystal growth.

1.Silicon carbide (SiC) is a covalent ceramic with strong Si–C bonds.
2.Key properties for high-temperature structural applications:
High strength and hardness even at temperatures >1600 °C.
Excellent oxidation resistance due to formation of protective SiO₂ layer.
Low thermal expansion → good thermal shock resistance.

Other options:
(খ) Continuous liquid phase → undesirable; SiC is a non-oxide ceramic, does not form liquid phases in service.
(গ) Higher thermal expansion → would increase thermal stress, not beneficial.
(ঘ) Plastic deformation → ceramics are brittle; SiC does not plastically deform easily.

1.Cement production is highly energy-intensive, requiring high temperatures (~1450 °C) in the kiln.
2.In Bangladesh:
Domestic energy sources (coal, natural gas) are limited.
Many cement plants rely on imported coal or petcoke, which increases production cost and supply risk.

Other factors:
(ক) High-grade limestone → Bangladesh has abundant limestone, but this leads to competition, not a critical operational challenge.
(খ) Excessive automation → not a major issue; labor availability is adequate.
(গ) Low demand → construction activity in Bangladesh is growing; demand is not minimal.

1.In the dry process of cement production, raw materials (limestone, clay) are ground into a fine raw meal.
2.The preheater and pre-calciner system:
Preheats the raw meal using hot gases from the kiln → raises temperature to ~800–900 °C.
Partially calcines the limestone (CaCO₃ → CaO + CO₂) before entering the rotary kiln.
3.Benefits:
Reduces fuel consumption in the main kiln.
Improves thermal efficiency and throughput.

Other options:
(ক) Clinker formation temperature ~1450 °C, not 1600 °C; preheater doesn’t increase final kiln temperature.
(খ) Free lime control → achieved by kiln operation and proper burning, not directly by preheater.
(ঘ) Grinding efficiency → depends on mill design, not preheater.

1.Ordinary Portland Cement (OPC) consists mainly of:
C₃S (Tricalcium silicate) → 50–70%
C₂S (Dicalcium silicate) → 15–30%
C₃A (Tricalcium aluminate) → 5–10%
Gypsum → 3–5% (added to control setting)
2.C₃S is responsible for early strength development because:
It hydrates quickly with water:
2C₃S+6H→C₃S₂H₃+3Ca(OH)₂
Releases significant heat of hydration → accelerates initial strength gain within 1–7 days.

Other options:
C₂S → reacts slowly → contributes to long-term strength (28 days and beyond).
C₃A → influences setting time and sulfate reactions, minor effect on strength.
Gypsum → mainly controls setting, not strength directly.

1.Caustic soda (NaOH) production in Bangladesh faces major limitations due to:
Poor quality of natural brine (impurities like Mg²⁺, Ca²⁺) → reduces efficiency of electrolytic cells.
Environmental restrictions → mercury cell technology (historically used) is highly polluting; strict regulations limit its use.

Other options:
(খ) Low demand → there is moderate demand in textiles, soaps, pulp, and paper, so this is not the main barrier.
(গ) Electricity → available for large plants; cost is a concern but not the main limiting factor.
(ঘ) Soda ash imports → affects market competition, but local production is mainly restricted by feedstock and environmental issues.

1.Mercury cell caustic soda plants use mercury as the cathode in the electrolysis of brine.
2.Critical by-product/environmental issue:
Mercury loss or spillage → highly toxic, persistent in the environment.
Plants must recover and recycle mercury to prevent contamination of water, soil, and air.

Other issues:
(ক) Chlorine gas → safely captured and sold; not the critical environmental concern.
(খ) Sodium carbonate waste → minor by-product; manageable.
(ঘ) Ammonia emissions → not relevant in caustic soda electrolysis.

1,In the membrane cell process for caustic soda production:
A cation-exchange membrane separates the anode (chlorine side) from the cathode (NaOH side).
The membrane selectively allows Na⁺ ions to pass from the brine/anode compartment to the cathode compartment.
OH⁻ ions remain in the cathode compartment, while Cl⁻ ions stay in the anode compartment, preventing Cl₂ contamination in NaOH.
2.This selective migration ensures:
Pure NaOH solution at the cathode.
Chlorine gas at the anode.

Other options:
(ক) Only OH⁻ → incorrect, OH⁻ does not pass through the membrane.
(গ) Both Na⁺ and Cl⁻ → incorrect, Cl⁻ is blocked.
(ঘ) Only Cl⁻ → incorrect, Cl⁻ is blocked.

1.In the diaphragm cell process for caustic soda production:
A porous diaphragm separates the anode and cathode compartments.
Brine (NaCl solution) flows through the anode compartment.
OH⁻ ions form in the cathode compartment, producing NaOH solution.
2.Limitation:
The porous diaphragm cannot prevent Cl⁻ back-migration completely, which would contaminate NaOH.
As a result, the concentration of NaOH is limited to ~10–12% w/w.
To obtain higher concentrations, evaporation or membrane cells are used.

Other options:
30–32%, 50–52%, 70–72% → achievable only with membrane cell or post-evaporation.

PMMA (Polymethylmethacrylate), also known as acrylic glass, is commonly used as a glass substitute because:
It is much lighter than glass (about half the density).
It offers excellent optical clarity, transmitting over 90% of visible light.
It has good UV resistance, so it doesn’t yellow quickly under sunlight.
It is more impact-resistant than glass, reducing breakage.

Other options:
(ক) Thermal resistance → PMMA softens around 100 °C, far lower than glass.
(গ) While chemically inert, its impact strength is not the highest among all plastics.
(ঘ) PMMA cannot withstand very high compressive loads; it deforms under stress more easily than glass.

Polypropylene (PP) tacticity refers to the arrangement of methyl groups (-CH₃) along the polymer chain:
Isotactic PP → all methyl groups on the same side of the chain.
Highly crystalline → strong, stiff, high melting point (~170 °C).
Used in fibers, films, and structural components.
Syndiotactic PP → methyl groups alternate sides.
Also semi-crystalline → good clarity, flexibility.
Atactic PP → methyl groups randomly arranged.
Amorphous, sticky, low strength, low melting → used in adhesives, sealants.

Other options:
(খ) Atactic PP → amorphous, not suitable for structural use.
(গ) Syndiotactic PP → semi-crystalline, not amorphous, melting point ~130–140 °C.
(ঘ) False → tacticity strongly influences mechanical and thermal properties.

High-Impact Polystyrene (HIPS) is a toughened version of polystyrene:
Pure polystyrene is brittle due to its rigid aromatic backbone.
HIPS is made by grafting polystyrene onto dispersed rubbery polybutadiene particles.
The rubbery domains absorb impact energy, preventing crack propagation → significantly improves impact resistance.

Other options:
(ক) Copolymerizing with methyl methacrylate → produces styrene–MMA copolymers, not HIPS.
(গ) Adding plasticizers → improves flexibility but not impact toughness significantly.
(ঘ) Higher polymerization temperature → may affect molecular weight, but PS remains amorphous and brittle; crystallinity is minimal.

Kraft process (sulfate process) and Sulfite process are both chemical pulping methods, but:
Kraft process:
1.Uses sodium hydroxide and sodium sulfide.
2.Can process hardwoods and softwoods.
3. Produces stronger fibers, ideal for paper, packaging, and specialty papers.
4. Efficient chemical recovery system.
Sulfite process:
1.Uses sulfurous acid and bisulfite salts.
2.Produces softer, weaker fibers, mainly from hardwoods.
3.Chemical recovery is more challenging.

Other options:
(ক) Lower lignin but weaker fibers → characteristic of sulfite pulp, not Kraft.
(গ) Kraft requires chemical recovery; Sulfite generates less effluent only in some variants.
(ঘ) Kraft is energy-intensive due to chemical recovery and digestion.

In the viscose process for rayon production:
1.Cellulose (from wood pulp or cotton linters) is treated with NaOH → forms alkali cellulose.
2.Carbon disulfide (CS₂) reacts with alkali cellulose → forms cellulose xanthate, which is soluble in dilute NaOH.
3.The viscous solution (viscose) is then extruded into an acidic bath → regenerates cellulose fibers.

Other options:
(খ) CS₂ is not a general solvent; it chemically reacts to form xanthate.
(গ) CS₂ does not neutralize acid.
(ঘ) CS₂ is not a bleaching agent.

Pulp, paper, and rayon industries are water-intensive and generate polluted effluents:
High BOD/COD → organic load from wood and cellulose processing.
Chlorinated organics → from bleaching with chlorine or hypochlorite (e.g., chlorinated lignins, dioxins).
Large water usage → affects rivers and local water resources.

Other options :
(ক) Nitrogen oxide emissions → more relevant to thermal power plants or petrochemical cracking.
(খ) CO₂ from clinker → cement industry.
(গ) Mercury contamination → mercury-cell caustic soda production.

1.Saponification (hydrolysis of triglycerides with alkali) produces soap and glycerine:
Triglyceride+3NaOH (or KOH)→3Soap molecules+Glycerol
2.Soap molecules+GlycerolYield of soap and glycerine depends mainly on:
Temperature → higher temperatures speed up reaction but excessive heat can degrade glycerine.
Reaction time → insufficient time → incomplete hydrolysis → lower yield.

Other factors:
(ক) Type of alkali → NaOH vs KOH affects soap hardness, not the overall yield significantly.
(গ) Color of fat → irrelevant; may affect appearance.
(ঘ) Atmospheric pressure only → saponification occurs at atmospheric pressure; pressure is not critical.

Builders are additives in detergents that:
1.Bind calcium (Ca²⁺) and magnesium (Mg²⁺) ions in hard water → prevents them from forming insoluble salts with the surfactant.
2.Enhance cleaning efficiency by allowing surfactants to work effectively.
Sodium tripolyphosphate (STPP) is a common builder that:
1.Chelates hardness ions.
2.Maintains alkalinity.
3.Improves detergency, especially in hard water conditions.

Other options:
(খ) Foam stability → mainly determined by surfactant type, not builders.
(গ) Fragrance retention → unrelated to builders.
(ঘ) Reduce pH → STPP is alkaline, so it does not reduce pH.

In soap production, the hydrolysis (saponification) of fats produces:
1. Soap (sodium or potassium salts of fatty acids)
2,Glycerine (by-product)
Glycerine separation by vacuum distillation is used because:
1. Glycerine has a high boiling point (~290 °C).
2.Direct heating at atmospheric pressure would cause decomposition.
3. Vacuum lowers the boiling point, allowing glycerine to be distilled safely and efficiently.

Other options:
(ক) Increasing saponification value → unrelated.
(খ) Neutralizing excess alkali → done by acid or soap refining, not distillation.
(ঘ) Removing free fatty acids → usually done by washing or neutralization, not distillation.

Vegetable tanning is the traditional method of tanning leather using natural tannins extracted from plants, such as:
1.Tree barks (oak, mimosa)
2.Leaves (myrobalan)
3.Fruits and wood extracts
Mechanism:
1.Tannins bind to collagen fibers in hides → stabilizing them and making them less water-soluble and more durable.

Other options:
(ক) Chromium salts → used in chrome tanning, not vegetable tanning.
(গ) Sulfuric acid → not used as a tanning agent.
(ঘ) Synthetic polymers → used in synthetic or modern tanning, not traditional vegetable tanning.

Chrome tanning uses chromium(III) salts, which:
1.Rapidly crosslink collagen fibers.
2.Produce leather that is soft, supple, and flexible.
3.Offers good water resistance and dimensional stability.
Applications:
1. Ideal for garments, gloves, upholstery, handbags, and jackets.

Other options:
(ক) Heavy-duty belts and saddles → usually vegetable-tanned leather, which is firmer and stiffer.
(খ) Shoe soles → often vegetable-tanned for durability.
(গ) Only decorative → chrome tanning is functional, not just decorative.

In leather processing, the initial step after obtaining raw hides is liming, which involves:
1.Treating hides with alkaline solutions (usually Ca(OH)₂) sometimes with sodium sulfide (Na₂S).
Purpose:
1. Swells the hide
2.Loosens hair and epidermis → facilitates hair removal (depilation)
3.Removes flesh and residual proteins
Other steps:

(ক) Tanning → stabilizes collagen fibers to produce durable leather; occurs after liming and tanning preparations.
(গ) Dyeing → adds color to tanned leather.
(ঘ) Finishing → applies surface coatings for aesthetics and protection.

Hexane is the most commonly used solvent in large-scale vegetable oil extraction because it offers:

High oil solubility → Efficiently extracts oil from seeds.
Low boiling point (≈69 °C) → Easy to recover by simple distillation.
Low cost and availability → Economical for industrial-scale operations.
Non-polar nature → Selectively dissolves oil while leaving proteins and carbohydrates in the seed cake.

Other options:
ক) Acetone → Soluble in oil, but highly volatile, flammable, and more expensive; not suitable for large-scale extraction.
খ) Ethanol → Polar solvent; less selective for oil and extracts more impurities like sugars and proteins.
ঘ) Benzene → Efficient but toxic and carcinogenic; banned for food oil extraction.

1.The first step in edible oil refining is usually alkali refining (neutralization).
2.Objective: Remove free fatty acids (FFA) from crude oil to prevent rancidity and improve stability.
3.Process:
Crude oil is treated with an alkali solution (usually NaOH or KOH).
Free fatty acids react with alkali → form soapstock.
Soapstock is separated from the oil → leaving neutral oil.

Other options:
ক) Bleaching → Removes color pigments, trace metals, and impurities; done after neutralization.
গ) Winterization → Removes waxes or high-melting triglycerides to prevent cloudiness; done later.
ঘ) Deodorization → Steam distillation at high temperature to remove volatile odor compounds; final refining step.

Bleaching is a refining step after neutralization in edible oil processing.
Main objectives:
Remove color pigments – carotenoids, chlorophyll, and other natural pigments that affect appearance.
Reduce peroxides – traces of oxidized compounds that can cause rancidity.

Other options:
ক) Free fatty acids → Removed during alkali neutralization, not bleaching.
গ) Glycerol and phospholipids → Mostly removed during degumming.
ঘ) Waxes and sterols → Waxes are removed during winterization, and sterols are generally left in the oil.

Bituminous Paints:
1.Made from bitumen (asphalt) dissolved in organic solvents, sometimes with added fillers or pigments.
2.Primary use: Provide waterproofing and corrosion protection for metals and concrete surfaces.
3.Common applications include: pipelines, tanks, bridges, metal roofs, and underground structures.

Other options:
ক) Decorative interior walls → Bituminous paints are dark, sticky, and not suitable for aesthetics.
খ) Automotive enamel → Automotive paints require glossy, durable, chemically resistant coatings, not bitumen-based.
ঘ) Floor coatings → Floors need abrasion-resistant and decorative coatings like epoxy or polyurethane; bituminous paints are unsuitable.

Varnish is a clear, transparent coating used to protect and enhance the appearance of surfaces (wood, metal, etc.).
Composed mainly of:
Resin → Film-forming agent; provides hardness, gloss, and protective barrier.
Solvent → Dissolves the resin for easy application; evaporates during drying.
Oil or plasticizer → Provides flexibility.
Optional additives → Anti-oxidants, dryers, UV stabilizers.

Other options:
খ) Pigment → Gives color or opacity; not part of a transparent varnish.
গ) Solvent → Evaporates during drying; does not form the protective film.
ঘ) Filler → Provides bulk or texture; not essential for film formation.

Spirit Varnishes:
1.Also called alcohol-based varnishes.
2.Made by dissolving natural resins (like shellac) in alcohol.
3.Fast drying (due to rapid alcohol evaporation).
4.Forms a hard, glossy, and transparent film.
5.Commonly used on wood and furniture.

Other options:
ক) Water → Used in water-based or acrylic varnishes, not traditional spirit varnishes.
গ) Mineral oil → Used as a plasticizer or in oil varnishes, not as the main solvent.
ঘ) Turpentine → Used in oil-based varnishes for dissolving resins and oils; not in spirit varnishes.