<span>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.</span>
<span>The answer is letter d. proof. </span>