The correct answer is: D. Postulate
A postulate is a statement that is assumed to be true without proof. It is a basic principle or assumption that is used to support other statements. Postulates are often used in mathematics and logic.
A doctrine is a set of beliefs or principles that are taught or accepted by a group or organization. Doctrines can be religious, political, or philosophical.
A maxim is a short, pithy statement that expresses a general truth or principle. Maxims are often used in proverbs and sayings.
A tenet is a principle or belief that is held to be true by a particular group or organization. Tenets are often religious or political in nature.
In the context of the question, a postulate is the most likely answer because it is a statement that is assumed to be true without proof. The other options are all statements that can be supported by evidence or argument.