Which of the following statements is correct?
a. the thesis statement belongs at the bottom of the pyramidal writing structure, while topic sentences belong at the top.
b. a topic sentence is typically placed at the end of the first paragraph.
c. a topic sentence should state what you want to say about the overall topic.
d. supporting sentences should "prop up" a topic sentence, while topic sentences should relate to the thesis statement.

The answer is D. Supporting sentences should "prop up" a topic sentence, while topic sentences should relate to the thesis statement. 

A is false because the "base" is the fundamental facts, not the topic sentences.
B is incorrect because a topic sentence is usually at the beginning of the three middle paragraphs.
C is false because a topic sentence should be about one particular aspect of an overall topic, not a large, branching statement.

Hope this helps!

Writing since he was a writer