In a paragraph, what is the purpose of the topic sentence?

• A. To state the main idea of the paragraph.
• B. To provide the author’s background.
• C. To list all supporting details.
• D. To conclude the paragraph.

Answer: (A)

The topic sentence names the main idea of the paragraph and sets the focus for what follows. It signals to the reader what the paragraph will be about, so all the other sentences work to explain, prove, or illustrate that idea.

This is why it’s the best answer: when you know the main idea right away, you can see how each sentence supports it with details, examples, or explanations, keeping the paragraph unified and easy to follow. The other roles described—giving background information, listing every supporting detail, or wrapping things up—happen in different parts of the paragraph and aren’t what the topic sentence is doing. A handy tip is to look for the sentence that states what the paragraph is mainly about; that sentence is the topic sentence.