The article is about Captain Kline
Because the first line talks about him and all of the other sentences talk about him.<span />
D. is wrong. It should be "One hero in the animation field is Mel Blanc, the voice behind many cartoon characters." because the information after Mel Blanc is not necessary to the sentence. It's just extra, so you need a comma.
He sees both the extraordinary quality of hope that Gatsby possesses and his idealistic dream of loving Daisy in a perfect world