Answer: c. insane
The narrator of this excerpt complains that other people characterize him as insane (<em>"why will you say that I am mad?"</em>) and he wants to deny the credibility of this claim. He says that he might be nervous, but he is not mad. In fact, his senses are sharper than ever, as he can hear everything, including what goes on in Heaven and Hell. This fact, intended to convince us of his sanity, proves that he is indeed insane.
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Answer: Age
Explanation: Age always goes up, but doesn't go down.
As far as I understood, your answer is the very last option