Correct Option: C

Charvaka is a system of Indian philosophy that assumes various forms of philosophical skepticism and religious indifference. It is characterized as a materialistic and atheistic school of thought. While this branch of Indian philosophy is today not considered to be part of the six orthodox schools of Hindu philosophy, some describe it as an atheistic or materialistic
philosophical movement within Hinduism. It emerged as an alternative to the orthodox Hindu schools, as well as a philosophical predecessor to subsequent or contemporaneous nastika philosophies such as Ajivika, Jainism and Buddhism.