Astatement that is assumed to be true is a
a. definition.
b. postulate.
c. theorem.
d. proof.

Definition is the formal statement of the meaning or significance of a word. Postulate suggests or assumes the existence, fact or truth of something as a basis for reasoning, discussion or belief. A theorem is a statement that can be demonstrated to be true by accepted mathematical operations and arguments. Proof is an evidence or argument establishing or helping to establish a fact or the truth of a statement. The answer is letter d. proof.