Hi @the66guy, let's take a look at the two answers. The question stem is asking for us to explain why the author references the work of two scientists around line 44.
C gives us a very general explanation for the author's decision. This is to give an example of something that Carol and Chen's theory would mean is true.
D is more specific, saying that the author includes the reference in order to show that an apparent issue in the theory can actually be explained by the theory.
I hope this clears it up a bit and helps you to see the right answer!
