Answer:
D. Directly stated themes
Explanation:
Because they will be directly talking about someone in their book
Based on the given sentence above, I can say that it is a compound sentence. What makes this sentence compound is that, it consists of two independent clauses and are connected by a coordinating conjunction "so". Therefore, the answer for this would be the last option: two independent clauses.
The correct is answer is A: The main idea of your essay
Hope this helps!