Answer:
The statement that would best serve as a topic sentence for a paragraph is A) Walt Whitman changed the way Americans thought of poetry.
Step-by-step explanation:
A topic sentence has the goal of informing readers on what the paragraph is about. It works as a map of the paragraph, letting readers know where you are going and how you are getting there in terms of the idea being developed. The sentences that come after the topic sentence function as its support, as evidence to defend the topic.
The reason why option A serves best as a topic sentence is the fact that it is more general than the others, allowing for its development throughout a paragraph. How come Walt Whitman changed the way Americans thought of poetry? The rest of the paragraph shall unveil the answer to that.
As for the other sentences, they would serve best as evidence to a topic sentence. B could be explaining why Robert Frost is considered a great poet; C could be detailing where Emerson got inspiration from; and D could be offering insights on Franklin's life history.