why is answer choice C is better than answer choice D?

@Samantha-Alexis, Happy to help. Let's take a look at (C) and (D). We're looking for the answer that tells us the primary purpose of the passage. (C) says, "refute an argument about the factors influencing black economic progress" In reading the passage, the main point is to refute a causal argument and to support an alternative one. The whole purpose of the passage is geared toward explaining why the continuous change hypothesis is incorrect, and (C) paraphrases this nicely. (D) says, "describe black economic progress before and after the 1960s" The problem with (D) is that the author was not describing black economic progress in a neutral manner; rather, she was refuting the ideas of the continuous change hypothesis theorists. Thus, we can get rid of (D). Does this make sense? Let us know if you have any questions!

This is great Ravi! Spot on, I had to think a little bit with C and B. It is clear that the author was refuting an argument.

Happy this helped! :)