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:T593,

The correct sentence is: ঘ) He said that he could finish the work that day.

Direct Speech থেকে Indirect Speech করার ক্ষেত্রে,
Direct Speech এর Reporting verb টি past tense এ হওয়ায়, Reported speech ও past tense এ হবে।
reported speech এর will এর পরিবর্তিত হয়ে would হবে, can হবে could.
Example
- Direct Speech: He said, 'I shall/will be unable to come.'
- Indirect Speech: He said that he would be unable to come.

Other options
ক) He said that he will finish the work that day.
এখানে will ব্যবহার করা হয়েছে, কিন্তু direct speech past tense হওয়ায় indirect speech-এ tense backshift করা উচিত।

খ) He said that he will be finished the work that day.
এখানে passive/tense ভুল; “will be finished” ব্যবহার করা হয়েছে যা সঠিক নয়।

গ) He said that he can finish the work that day.
এখানে can ব্যবহার করা হয়েছে, যা present/future ability বোঝায়, কিন্তু past tense context-এ could ব্যবহার করা উচিত।