Person who believes that God is every thing and everything is god

Answer: Option C

One word substitute is Pantheist.

Agnostic: a person who believes that nothing is known or can be known of the existence or nature of God.
Theist: a person who believes in the existence of a god or gods, specifically of a creator who intervenes in the universe.
Pantheist: person who believes that reality is identical with divinity, or that all-things compose an all-encompassing, immanent god.
Pantechnicon: a large van for transporting furniture.