The antonym of 'atheist' is--

The question is asking you for the opposite word for the term 'atheist'. An atheist is someone who does not believe in the existence of God or gods. So, the opposite of an atheist would be someone who does believe in God or gods. Among the choices given, the word 'believer' is the one that best fits this definition. Agnostic refers to someone who believes that the existence of God or gods is unknown or unknowable, Idealist refers to someone who sees things in their ideal form, and Non-believer refers to someone who does not believe in a particular religion or concept of God. Therefore, 'believer' is the correct answer to the given question.