A: to express the central idea of a paragraph. The purpose of a topic sentence is to clearly state the main point or central idea of a paragraph. It helps to guide the reader and sets the tone for the rest of the paragraph.
The purpose of a topic sentence in a paragraph is to express the central idea of that paragraph. It serves as a summary of the main point or theme that will be discussed in the paragraph. This helps readers understand the main focus of the paragraph and provides them with a clear direction before reading further. By reading the topic sentence, readers can quickly grasp the subject matter and decide whether they want to continue reading the rest of the paragraph. The topic sentence should be concise, clear, and assertive in order to effectively convey the main idea. Therefore, the correct answer is A: to express the central idea of a paragraph.
