What is a common phrase or saying called?

The correct choice refers to the term "proverb," which describes a common phrase or saying that expresses a general truth or advice based on common sense or experience. Proverbs are often passed down through generations and are typically known for their concise and memorable nature.

A "maxim" is similar in that it conveys a rule of conduct or a principle, but it does not always express a common truth in the same way that proverbs do. An "axiom" is a statement regarded as self-evidently true and is usually used in mathematical or philosophical contexts. A "thesis" refers to a statement or theory that is put forward as a premise to be maintained or proved, typically in academic writing.

Understanding these distinctions helps clarify why "proverb" is the most appropriate term for a common phrase or saying.