Question

choose the poem that uses assonance.
there is a bird in the poplars—
it is the sun!
the leaves are little yellow fish
swimming in the river.

some pearly shell, the castaway
of indefatigable seas
on a shingle far away—
you will not tell, we cannot know.

from william carlos williams, \metric figure\ and adapted from robinson jeffers, \to an old square piano\

Explanation:

Assonance is the repetition of vowel sounds within words. In the second poem ("Some pearly shell, the castaway..."), we see vowel repetition: in "pearly" and "shell" (vowel sound /ɜː/ or similar in some accents), "indefatigable" and "seas" (vowel sound /iː/), "shingle" and "far" (less strong, but more notably "will not tell, we cannot know" has repeated short vowel sounds in "will", "not", "tell", "we", "cannot", "know" – the short /ə/ or /ɒ/ /ə/ etc. The first poem has less vowel repetition. The second poem's lines like "You will not tell, we cannot know" have repeated vowel sounds (e.g., the short vowel in "will", "not", "tell", "we", "cannot", "know" – the /ə/ or similar short vowels, and also in "pearly", "shell", "indefatigable", "seas" etc. So the second poem (with lines "Some pearly shell, the castaway...") uses assonance.

Answer:

The poem with the lines: "Some pearly shell, the castaway
Of indefatigable seas
On a shingle far away—
You will not tell, we cannot know."