The best response to the question regarding how the structure of the poem affects its meaning is:
The use of three quatrains gives a consistent, ordered quality to the speaker’s whimsical descriptions of the dream.
This option highlights how the structured format contributes to the overall dreamlike quality of the poem, reinforcing the themes of fantasy and imagination present in the speaker's experience. Each quatrain contributes to a cohesive image of the dream landscape, enhancing the poem's whimsical nature.