Out of the options given below, choose the one which can be substituted for the given expression-

A person who does not believe in God

Atheist

The correct answer is Option (2) → Atheist

An atheist is a person who does not believe in the existence of God.

Option (1) → Theist: A person who believes in the existence of God or gods.
Option (3) → Ascetic: A person who lives a simple and disciplined life, often for spiritual reasons, but not necessarily without belief in God.
Option (4) → Altruist: A person who is selflessly concerned for the welfare of others.