You're correct! The key characteristic of a refrain in a poem is repetition (option c). A refrain is a line, phrase, or stanza that is repeated at regular intervals throughout a poem. This repetition is often used to emphasize an idea, create a rhythm, or evoke a certain mood. When analyzing poems, it's important to look for patterns and repeated elements, such as refrains, to understand their significance in the overall meaning of the poem.
