Singular :

A. Dull

B. Ancient

C. Common

D. Social

Answer: Option C

Solution(By Examveda Team)

Dull : lacking interest or excitement.
Ancient : belonging to the very distant past and no longer in existence.
Social : relating to society or its organization.
Common : occurring, found, or done often, prevalent.
Singular : exceptionally good or great; remarkable.

Antonym of Singular is Common.