Option d is the correct answer. Vaisheshika is a school of Indian philosophy that propounded the atom theory. Vaisheshika postulates that reality consists of six categories: substance, quality, action, generality, particularity, and inherence. Vaisheshika also proposes that atoms are the smallest indivisible units of matter, and that they combine to form complex entities. Vaisheshika aims to achieve liberation (apavarga) by freeing oneself from ignorance and attachment.