As always, let’s start with the question stem. We are looking a description of the view held by critics whom the author criticizes as holding an “inverted snobbery†position.
Thankfully, we get a line citation (line 17) so we can zoom in and see what the passage says. The author writes that “Others find [James] pretentious and tiresome; an inverted snobbery accuses her of abandoning the time-honored conventions of the detective genre in favor of a highbrow literary style.â€
So the critics find James’ writing pretentious because it abandons time-honored detective conventions in favor of highbrow literary style. The snobbery is inverted because the critics don’t want highbrow — they want lowbrow, regular, detective novels.
And that is exactly what answer D states: Detective fiction should be content to remain an unambitious litera genre (rather than strive for highbrow literary style!)
I hope that helps. Please let us know if you have further questions.