Question

Joseph Addison says in his essay "Argument" that it is best to remain polite and calm during an argument.

Answer 1

B and A look like good answers, but the meaning of candor is "unbiased, impartial"; and although that seems like a good answer it is not because the question does not ask you about a quote that talks of entering an argument, simply being in it. So, I would definitely say that the answer is A. :)

Answer 2

A is the best answer and only answer