The answer is A. "The Negro lives on a lonely island of poverty".
If you want the short answer: I had the same question on my test.
If you want the long answer:
By using this sentence, we are provided with vivid imagery of black American citizens being isolated from the rest of America due to their skin color and the poverty caused by their skin color.
Black American citizens were, at the time, and still sadly sometimes viewed the same today, as a low society. They were separated from white American citizens, deemed unfit and unqualified for proper work, thus many lived in poverty.
This served as a separation between white American citizens and black American citizens, thus it felt as if black people lived on a separate, lonely island accompanied by nothing only than poverty.
