The correct option is B witty
The word that would fit the most ion the given blank is option B, Witty. Witty is used for someone who is very quick in using clever and funny words. The context of the sentence is that it was impossible for the person to put out of his mind the witty words he heard from his clever father-in-law. Option A, 'inspiring' means encouraging. Option C, 'sarcastic' means using words opposite to that of what the person means in order to hurt the other person. Option D, 'soothing' means having a calming effect. Option E, 'exhortative' are the words intended to encourage. Thus, options A, C, D and E are incorrect to be used in the blank and the best fit is Option B, 'Witty'.