According to "the philosophy of composition," what was the purpose of the refrain in "the raven"?

a. to serve as a pivot point for the poem

b. to give the poem a pleasing rhythm

c. to make the poem longer

d. to give the reader a break

The first item is correct (A).

In The Philosophy of Composition, Poe explains how he came to resources that  set the desired tone and showed how the phonetic elements  were combined to construct the form from which the meaning would be extracted in The Raven.

According to him, it was possible to establish definitively the rhythm, the meter, the extension and the general arrangement of the resort in question, as well as those that would precede it.

hi i’m sorry to call y’all today i is a time for you