Though he worked very hard . . . . . . . . he could not get the highest marks.

A. in spite

B. also

C. but

D. yet

Answer: Option D

Solution(By Examveda Team)

When 'though' is used with a verb in the subjunctive mood (expressing doubt, a condition contrary-to-fact, a wish, a concession) is followed by 'yet' and not by but.
Example: Though he might not have recognized me, yet it is rude of him.