In this question we are looking for something that the passage claims Eltis disagrees with, so this is something that should have strong textual support. We begin to discuss Eltis around line 30.
From the final paragraph, we are told that Eltis is mostly opposed to the thesis outlined in paragraph 2, that of Drescher. This means that Eltis is arguing against the core of Drescher's argument- which is that political action and a popular, populist conception of personal liberty was mostly responsible for the antislavery movement.
Since Eltis argues against Drescher, and C is a good match for Drescher's argument- we do have a good deal of support for C.
