14:I[5014,["/_next/static/chunks/11d1gk4m2o846.js","/_next/static/chunks/14mrh2-p_w84d.js","/_next/static/chunks/40y9lkvta2o_p.js"],"default"] 15:I[38392,["/_next/static/chunks/11d1gk4m2o846.js","/_next/static/chunks/14mrh2-p_w84d.js","/_next/static/chunks/40y9lkvta2o_p.js"],"PracticeCard"] 17:I[70570,["/_next/static/chunks/11d1gk4m2o846.js","/_next/static/chunks/14mrh2-p_w84d.js","/_next/static/chunks/40y9lkvta2o_p.js"],"ExamAppearanceBadge"] 16:T539,Supposition (noun)
English Meaning: An idea that something may be true, although it is not certain.
Bangla Meaning:
(১) [uncountable noun] অনুমান; কল্পনা: Your theory is based on mere supposition.
(২) [countable noun] অনুমান; আন্দাজ; আঁচ: His suppositions were proved false.
on this supposition; on the supposition that ...যদি ধরে নেওয়া যায় যে…।
Synonyms: Suspicion (সন্দেহ; সংশয়; অবিশ্বাস), Belief (বিশ্বাস; আস্থা), Assumption (অনুমান).
Antonyms: Fact ((প্রকৃত) ঘটনা), Certainty (নিশ্চয়তা), Assurance (আত্মপ্রত্যয়; আত্মবিশ্বাস).
Other Forms: Suppositional (adjective).
Example Sentence: ‘They were working on the supposition that his death was murder.’

The given words, Supposition, Assumption, and Suspicion all convey almost similar meanings.
On the other hand, 'Certainty' is the antonym of 'Supposition'.
Therefore, the word 'Certainty' is the odd one out among all and hence it is the incongruous one.

Source: Live MCQ Lecture