C.
Why A and D do not work: A thesis is not plot.
Why B does not work: A thesis is not a description of the type of the book.
Answer: Structure is a constructed building or a specific arrangement of things or people, especially things that have multiple parts. An example of structure is a newly built home. An example of structure is the arrangement of DNA elements. Something composed of interrelated parts forming an organism or an organization.
Explanation:
They need to read more of the authors writings to find the key to the story's truths.