Answer: D

Explanation:

Mortal means someone who has to die or cannot live forever, e.g., humans. So, its antonym is immortal which means never dying, living forever.

Answer: C

Explanation:

Luminous means glowing, shining, etc. So, its antonym is Dim as it means dark or dull.

Answer: D

Explanation:

A pit is a hole, cavity, etc. So, its antonym is peak which refers to the top of a mountain or hill.

Answer: A

Explanation:

‘Rotund’ means curved or round. So, out of the given options, only thin can be its antonym as it means slender, slim, etc.

Answer: C

Explanation:

‘Common’ means ordinary, widespread, etc. So, its antonym is rare as it means unusual, uncommon or infrequent.