Thanks for the question! This question asks us for what passage B’s author thinks about opera pieces in which the words are subordinated to the music. For this, we’ll have to do a recap of chapter B. There are three types of opera, according to passage B’s author, and then the second paragraph says that we have to consider the opera as a whole. And so it’s not like one kind is better than the others, they’re all special in their own ways. And so (D) is certainly correct, the author thinks it’s a legitimate type of opera.
Hope this helps! Feel free to ask any other questions that you might have.