What role do supporting details typically play in a passage?

Supporting details in a passage serve to explain and illustrate the main idea by providing additional information that clarifies, elaborates, or substantiates it. These details can take various forms, such as facts, examples, statistics, or anecdotes, which help to build a stronger understanding of the central theme or argument being presented. By doing so, they enhance the reader's comprehension and engagement with the text.

The other choices do not accurately reflect the role of supporting details. Summarizing the entire passage implies a broad overview rather than expansion on a specific main idea. Providing merely opinions would lack the necessary factual basis that supports the main point. Lastly, listing topics discussed in the passage does not delve into the details that enrich and support the main idea, which is the primary function of supporting details.