When a poet repeats a word, phrase, or grammatical structure in a social poem, the primary purpose is...

When a poet repeats a word, phrase, or grammatical structure in a social poem, the primary purpose is usually to
a.
signal that an idea is important enough to build pressure through return
b.
fill space within the poem and extend the overall length of the piece
c.
establish a rhyme scheme consistent with the poem's historical tradition
d.
indicate that the poet struggled to find fresh language for the concept