This question asks you to identify what's the author's purpose in using certain example in the passage.
“simultaneous abolition” was stated as a point that would have attracted more historians, but did not do so. (7-13)
Let's go to the answer choice.
A) Whether rebellions were the cause is not discussed.
B) Tocqueville is used as a historian who was likely to be studying this issue. “foresee” has nothing to do with him.
C) Just as we've discussed above, this is one possible reason many historians could have been attracted to this issue. (Correct)
D) Kolchin’s study has nothing to do with this. The author presented this just to make a point about not many historians were interested in this matter at the beginning of the passage, which act as an introduction to Kolchin's study, which is an independent study and what the author is mainly focused on using the rest of the paragraphs.
E) "underlying similarities" is not what the author is trying to do. He/she is using this to prove something else.