What is the main function of a topic sentence?

The main function of a topic sentence is to summarize the main idea of a paragraph. It serves as a guide for the reader, indicating the central theme or focus of the paragraph that follows. A well-crafted topic sentence allows readers to quickly understand what the paragraph will be about, providing clarity and direction for the supporting details that will elaborate on that main idea. By establishing this framework, the topic sentence helps maintain the coherence of the paragraph and ensures that all subsequent sentences relate back to this central point, reinforcing the overall argument or narrative. In contrast, other options like concluding a paragraph or providing background information do not adequately capture the primary role of a topic sentence.