Thanks for the question! We’re being asked here for something that most accurately expresses the main point of the passage here. (D) tells us that this main point is that the assertion that prions cause CJD has been received with great skepticism in the scientific community because it undermines a firmly entrenched view about the nature of pathogens.
So for something to be the main point, it has to both be supported by the passage, and also has to actually be the main point (as opposed to something just mentioned). Well, first of all, is this something that’s supported by the passage? Take a look at the last paragraph, which tells us that the link between prions and CJD was “initially” received with great skepticism in the scientific community, but subsequent research has supported the conclusion that prions are an entirely new class of infectious pathogens. So it seems like the assertion was a thing of the past. But (D) says that the assertion is still being viewed with skepticism, which is incorrect. So (D) can’t be the main point here.
Hope this helps! Feel free to ask any other questions that you might have.
