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.

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

A: microbiology
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Q: The woman didn't like to use a peeler to peel a pineapple, so she used her hands. The _ was hard to control.

A: peeler
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Q: The old man began to feel a dull pain in his joints, and knew that it was arthritis, because the _ were worn out.

A:
joints
****