Answer:
D. He uses rhetorical questions for emphasising his main point.
Step-by-step explanation:
In the excerpt given in the question from “speech to the convention of delegates of Virginia” the arguments are structured with the help of the rhetorical questions so that his main point is properly understood. The questions are asked for gaining the answers which would satisfy the instinct of the person. He is questioning his strength and the way in which it would come to them.