I think this one is difficult as well. I'll explain why Tamika is actually not arguing against a hypothesis.
Here is the hypothesis given in the second sentence: People are being duped by questionable medical products. Why? Because most people yearn for easy solutions but they don't have the medical knowledge to avoid fraud.
Now, this is why B is incorrect. Does that hypothesis make a claim about the behavior of everyone? No, it doesn't. It makes a claim about the behavior of most people. It also says that most people do not have medical knowledge, so it has already excluded medical professionals! She can make a separate argument about medical professionals, and it won't affect her hypothesis.
These statements can coexist. Tamika doesn't have to argue against that hypothesis. Rather, she seeks to explain the behavior of two groups: most people vs. medical professionals. This is why D is correct.