Vapidity means lacking or having lost life, sharpness, or flavor, becoming dull.
Hence option B is the correct answer because “dullness” means to be lacking excitement or interest, hence it is the correct answer.
Option A is incorrect because “provocativeness “ means the ability to provoke someone to do something, which is incorrect here because it is not the correct meaning.
Option C is incorrect because “agitation” means a state of nervous excitement which is not the correct meaning of the given word.
Option D is incorrect because “interesting” is an antonym to the given word.