You need to answer a given question containing a blank (_). Your answer must be one of the two objects mentioned in the question, for example "trophy" and "suitcase". Your answer must not contain a word that is not present in the question. Please don't use articles (e.g., the, a) before the answer.

Bob needed to shave both his beard and his eyebrows, but the _ was dense.
beard

The essay on microbiology was more interesting than the one written on statistics. _ must be an interesting subject.
microbiology

Amy wrote a letter to Kai to send a clear message, Kai replied Ami with a poem which was obscure, because of the _ Kai knew how Ami feels.
letter