What is the name for a claim or statement that expresses a person's opinion and must be supported by evidence?

The correct answer is that the term for a claim or statement expressing a person's opinion, which must be supported by evidence, is known as an argument. An argument goes beyond just stating a personal opinion; it involves presenting a position that is backed by reasoning and evidence to persuade others.

In the context of writing and discourse, an argument incorporates various elements, including a clear stance on an issue and supporting details that reinforce that stance. This makes it distinct from simple opinions, as arguments are structured to engage with counterarguments and provide a comprehensive case for one perspective.

While other terms like assertion and claim might refer to statements of opinion or belief, they lack the necessary depth of evidence and reasoning that characterizes an argument. Therefore, calling an opinion that requires support simply a claim or assertion does not capture the argumentative nature and structure of reasoning involved in effectively persuading an audience. A thesis, which usually represents the main idea or overarching claim in a piece of writing, also serves a different function, as it primarily summarizes the main point rather than engaging in a back-and-forth with evidence and reasoning like an argument does.