Manifest Destiny supporters would be in favor of D acquiring land west of the Mississippi river. Manifest Destiny is the belief that America should take land from the Atlantic to the Pacific ocean.
That is describing what the character does so it is C. It couldn't be A because it isn't a part of the story. It couldn't be B because it isn't a problem. It lastly couldn't be D because it's not a message the author is trying to convey to the reader.
Homer Plessy "<span>a. Sat on a railroad car designated for Whites," which the Supreme Court ruled as illegal in the case "Plessy vs. Ferguson," since this case upheld "separate but equal policies" in the US. </span>