Thanks for the question! Let’s take a look at the stimulus. We’re basically told that purebred dogs are more likely to have genetically determined abnormalities, which when corrected by surgery can be pretty expensive. Nonpurebred dogs rarely suffer from these, so the argument concludes that if you want to reduce the risk of incurring costly medical bills, you should pick a non purebred dog.
Now we’re asked for something that weakens the argument. Let’s take a look at (B), which tells us that all dogs are subject to the same non genetically determined diseases. This may be true, but that doesn’t change the fact that purebreds are still more likely to have these genetically determined problems. And (B) doesn’t tell us that non purebreds are more likely to get non genetically determined diseases. If they get those diseases at the same rate, then it just makes a baseline disease level that both share, but then purebreds are more likely to get genetically determined diseases—on top of their risk of non genetically determined diseases, they are more likely to have these genetically determined abnormalities. So if you want to reduce the risk, you should still avoid purebreds. Thus, (B) doesn’t really weaken the argument, and is the wrong answer.
Hope this helps! Feel free to ask any other questions that you might have.
