Who could possibly have believed him to be guilty? / yet today he is behind the bars in alcatraz.

the first member of the pair is a fragment, and the second is complete
the second is a fragment, and the first is complete.
both are complete.
both are fragments.

the correct answer is d. a discussion of specific uses of alliteration

.

when you are critiquing or evaluating a poem, you will mostly pay attention to the theme, as well as figures of speech and rhythm. alliteration is a figure of speech where consonants are repeated in neighboring words - and it is important for analysis of sound and rhythm, which is why it might appear in the evaluation of that poem.