Which of the following mandals of Rig Veda was dedicated to Soma ?

The correct answer is (c).

Soma is a Vedic deity associated with the moon and intoxicating drink. He is the subject of many hymns in the Rig Veda, the oldest Hindu scripture. The ninth mandala of the Rig Veda is entirely dedicated to Soma.

The other options are incorrect. The fifth mandala of the Rig Veda is dedicated to Indra, the god of war. The seventh mandala is dedicated to the Maruts, a group of storm gods. The tenth mandala is a collection of miscellaneous hymns.