The answer is D. A sentence that contains the main idea of a paragraph
Explanation:
In writing, topic sentences state the main point of each paragraph and are usually found at the beginning of these because they help the reader understand what is the content of each paragraph. This implies, in texts with multiple paragraphs such as essays there are multiple topic sentences, although these are related as they explain the main topic of the text. At the same time, topic sentences are explained and developed through details in the paragraph such as supporting sentences or examples. Thus, the last option is the one that defines a topic sentence.
