The correct answer is D. There is no single topic sentence.
Explanation:
A topic sentence is a sentence that summarizes the main idea of a paragraph, this sentence is usually the first sentence in the paragraph and states what the paragraph is about. On the other hand, the paragraph presented here deals with multiple topics or concepts including the Earth's crust, the plates, the Earth's mantle, volcanoes, earthquakes, and mountain ranges, this means the paragraph is related to geography but explores multiple ideas that are not summarized in any of the sentences presented in the paragraph, neither at the beginning nor at the end of it. Thus, as there is no any sentence or phrase that states what the paragraph is about as a unit or summarizes all the ideas of the paragraph there is no a single topic sentence because this paragraph includes multiples ideas that might be difficult to summarize in only one topic sentence.
