The correct option is D Vaisesika
The source of early Vedic Aryans for religious practices is mainly Rig Veda. The Rig Veda is dedicated to natural forces and treat them as various gods. Indra (god of rain), Agni (god of fire), Vayu (god of air), Varun (god of water) are certain examples. It is believed that worshiping these gods will bring prosperity and expansion of clan. In order to worship them, Yajnas or Ahutis (sacrifice) were performed in presence of fire by the Brahmins.