Answer and Explanation:
An alliteration is the repetition of sounds or letters at the beginning of words that are close to each other in a structure. I believe there are two lines in which alliteration can be found in the excerpt provided:
Too silver for a seam—
Or Butterflies, off Banks of Noon
In the first line, there is the repetition of the /s/ sound, while in the second one, of the /b/ sound. The words are in quick succession, close to each other, which makes the repetition even more noticeable.
NOTE: I was unable to find this question online to see what the options are. In case you should only choose one line, pick the second one - butterflies / banks.