Answer:
The correct answer is option A. Expository.
Step-by-step explanation:
A topic sentence is the most important thing in an expository text. Its function is to give a structure to the paragraph, summarizing it and leaving the main idea.
This sentence is the one that gives us a preview of what will follow in the text and is located as the first sentence.
On the other hand, an expository text is one that provides information objectively about a topic.