Final answer:
Whitman most likely chooses the free verse structure for his poem as it presents a conversational style and reflects the diverse voices and occupations of the American people.
Step-by-step explanation:
Whitman most likely chooses the free verse structure (C) for his poem. The free verse structure presents a conversational style, allowing the poem to flow naturally and reflect the diverse voices and occupations of the American people. Without the constraints of rhyme and traditional rhythmic patterns, the free verse structure also allows Whitman to express his unique poetic vision and celebrate the individualism and democracy he values. For example, the absence of a set structure in the poem mirrors the freedom and diversity of America and its people.