Thanks for the question! So let’s take a look at passage B near the beginning. Here, we’re told about how Cather talks about how she prefers to think of her work Death Comes for the Archbishop not as a novel, but instead as a narrative. Now look at (C), which tells us that Cather regarded at least one of her works as not fitting straightforwardly into the category of the novel. Well, this is exactly what (C) says. The work being referred to here is Death Comes for the Archbishop, and she is “asserting vehemently that it is not a novel,” or saying it doesn’t fit into the category of novel (lines 30-33). So since this is something that passage B is indicating, this is the correct answer choice.
Hope this helps! Feel free to ask any other questions that you might have.