The correct answer is B. overweening.
Overweening means excessively proud or self-confident. It is a negative trait that can lead to arrogance, conceit, and a disregard for others. In the context of the question, the man’s overweening vanity made it difficult for him to accept that anyone could disagree with him. He was so sure of his own superiority that he could not imagine that anyone else might have a valid point of view.
The other options are not as accurate descriptions of the man’s vanity. Overstrung means tense or nervous, which does not seem to be the case here. Overwhelming means too much to be dealt with, which is also not accurate. Overwrought means excessively emotional, which could be true, but it is not the most specific or accurate description.
Therefore, the correct answer is B. overweening.