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.

the installment plan of the 1920s, an arrangement that allowed people to buy what they wanted with a small down payment and pay off the rest in monthly installments, provided americans a way to own what they did not have the money to buy.

polisit can also mean a body of citizens. in modern historiography, polis is normally used to indicate the ancient greek city-states, like classical athens and its contemporaries, and thus is often translated as "city-state". the body of citizens came to be the most important meaning of the term polis in ancient greece.