The poetic devices that help to create rhythm in a poem are:
- assonance: the repetition of vowel sounds can create a musical quality and rhythm.
- alliteration: the repetition of consonant sounds at the beginning of words can also add to the rhythm and flow of a poem.
Similes and imagery, while valuable poetic devices, primarily serve to create comparisons and visual descriptions rather than directly contributing to rhythm. Therefore, the correct answers are assonance and alliteration.