What is the effect of the last stanza mimicking the first?
a) the speaker, disturbed from his sleep, is angered at the sudden tapping.
b) the tapping has become more dramatic, but the speaker has grown disinterested.
c) the speaker, while initially upset, is now calm in his approach to the tapping.
d) the tapping, which was seemingly innocent, is now seen as mysterious by the speaker.

D) The tapping, which seemingly innocent, is now seen as mysterious by the speaker.

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 The correct answer is :  D) The tapping, which was seemingly innocent, is now seen as mysterious by the speaker.

Explanation:  The importance of the last stanza is evident because there is a change that causes tension. This change makes the poem more frightening because, until the last stanza, the whole story seemed like something that had happened long before, but when the speaker changes to the present time, it is clear that this personal chaos will not end.