Thanks for the question! (B) is wrong because it’s just too narrow of an answer. It’s true that this somewhat happens in the first paragraph, but not really otherwise. The discussion about Duke Ellington isn’t really “contrasting†so much as showing similarities between their works. As a result, it’s a stretch to say contrasting works is the primary purpose of the passage.
As for why (C) is correct, we can see throughout that Toni Morrison’s novel is being discussed, and in particular, her drawing upon a musical genre as the structuring principle for the entire novel. This is a consistent theme throughout the entire passage, and so (C) is the correct answer.
Hope this helps! Feel free to ask any further questions that you might have.
