Why A?

The conclusion of the argument is: "potential dog owners who want to reduce the risk of incurring costly medical bills for their pets would be well advised to choose nonpurebred dogs." Why? We are told that purebred dogs are prone to genetically determined abnormalities. Though these abnormalities can often be fixed by surgery, they are very expensive. We also know that nonpurebred dogs rarely suffer from genetically determined abnormalities. Now, it's important to point out the unstated assumption in the argument. The assumption is that owners of purebred dogs must fix the abnormalities, and to do that they must incur the high costs of corrective surgery. Answer choice (A) states: "Most genetically determined abnormalities in dogs do not seriously affect a dog's general well-being." This answer choice directly attacks the unstated assumption. If the abnormalities do not seriously affect a dog's general well-being, then all the more reason not to have to spend several thousand dollars to correct the abnormality! If a purebred dog owner doesn't pay the exorbitant cost of the corrective surgery, then, according to the passage, owning a purebred dog will not be any more expensive than owning a nonpurebred dog. Answer choice (A) breaks down the connection between the premise and conclusion of the argument, i.e. weakens the argument. Thus, it is our correct answer. Hope that clears things up! Please let us know if you have any other questions.

Awesome, thank you

Your explanation makes sense. I wanted to see if you could clarify C and why that is incorrect. I chose C because if purebred dogs had a shorter lifespan than nonpurebred dogs, then I inferred that over an average lifespan, purebred dogs will cost less in medical bills than a nonpurebred dog. If this is true, this would thus weaken the argument and be correct. Am I making too far of a jump in the logic behind choosing C?

Yes, you cannot make that jump. What if a purebred dog had a shorter lifespan because of some genetic disease that require many trips to the vet? Then your assumption no longer stands. Never assume on the LSAT. If we have not been given information on it, then we know nothing about it. Hope that helps! Please let us know if you have any other questions.

But aren't you assuming in choosing A that the dog's well-being is the only or even primary reason the dog owner would seek corrective surgery? What if dog owners' only reason for seeking corrective surgery were cosmetic and had nothing to do with well-being. Then I don't see how A would weaken this argument...

@dannyod, Great question. (A) says, "Most genetically determined abnormalities in dogs do not seriously affect a dog's general well being." You're right, (A) is assuming that most dog owners would put have their dogs get corrective surgery only if it were for well-being. It's extremely likely that these dog owners wouldn't elect to have their dogs get surgery just for cosmetic reasons. The scenario you're describing, while possible, isn't a reasonable assumption that we can make. Think about it: how many people that you know have dogs? How many of them have their dogs get surgery for cosmetic purposes? It's simply not a realistic assumption. Even if you were to assume what you assume for (A), which of the other answer choices would you select? Each of them is worse than (A), and none of them actually weakens the argument. If the genetic abnormalities mentioned in the stimulus aren't life-threatening (for the most part), then the conclusion of this argument is wrecked, so (A) does weaken the argument. Does this make sense? Let us know if you have any other questions!

Thanks for the response Ravi! I see what you are saying, and agreed it's a bit of a stretch, but I guess I'm still having trouble discerning when common sense assumptions are appropriate on the LSAT and when they are not. I feel like sometimes LSAT questions use common sense assumptions as red herrings so the test taker mistakenly selects them (how I approached option A here), when really one should not take for granted what is not explicitly expressed in the question/passage. But it seems like in this question a common sense assumption is required to arrive at the correct answer. To your point about what other option might weaken, I selected C, which also isn't a great but seems like it could weaken (if you make another common sense assumption that shorter lifespan = less overall medical costs because there is less time the dog is alive and in need of medical care). This assumption seems just as reasonable as assuming that a dog's well-being is the only or primary motivation for seeking corrective surgery (i.e., what if most people with purebred dogs have them as show dogs? In selecting A we're actually reinforcing the fact that well-being isn't a primary factor). But maybe I'm overthinking this? Thanks for your help!

@dannyod, Great question. (C) says, "Purebred dogs tend to have shorter natural life spans than do nonpurebred dogs." The problem with (C) is that we don't know how much shorter purebred dogs' lifespans are. What if it's only a month or two? Additionally, if you assume that shorter life span means less medical costs, then you also have to make some other assumptions, including one that entails that medical costs for dogs' lives are distributed over the course of their entire life. Maybe most costs occur shortly after birth and right before death. If this were true, then life span might not have much of an effect on costs. The ambiguity of (C) of not knowing how much shorter purebred dogs live is what allows us to get rid of it. Even if we assume what you said you were assuming to be true, the dogs would have to live for an appreciably shorter amount of time in order for there to be a noticeable difference in medical costs. And, as mentioned above, if they're only living one or two months less (which is totally possible because of how vague (C) is worded), then the cost argument for shorter life spans leading to cheaper medical costs wouldn't hold. Ultimately, the assumption that's needed for (A) is a more reasonable one. Cosmetic surgery for dogs, even ones who are shown, isn't a thing. Most dog breeders focus on cosmetics when they're breeding dogs together. I know it can be difficult for some questions to tease out what types of assumptions are more reasonable than others, but ultimately with more practice, you'll continue to get better at it. When in doubt, think about the assumptions in relation to the facts and evidence you're given in the stimulus. For this question, (A) requires assumptions that are more reasonable than (C). Does this help? Let us know if you have any more questions!

Hello @Ravi or @ Melody, would you by chance be able to explain why B would not weaken, I understand the conclusion and method getting to A now. I would just like to understand the methodology getting away from what seemed to me now is a trap question like B.

@Jermaine1, I'm happy to help! The passage tells us that purebred dogs are prone to genetically determined abnormalities that are expensive to correct. Nonpurebred dogs rarely suffer from these genetically determined abnormalities. Therefore, the argument concludes that potential dog owners looking to reduce medical costs should choose nonpurebred dogs. We are asked to select an answer choice that will weaken this claim. (B) "All dogs, whether purebred or nonpurebred, are subject to the same common nongenetically determined issues." There are two reasons why I would rule out this answer choice. First, it seems irrelevant. The passage is only talking about issues that are genetically determined, not those that are nongenetically determined. Secondly, if anything, the more we think about this answer choice the more we see that it could possibly strengthen the argument in the passage. If purebred dogs are subject to genetic and nongenetic issues whereas nonpurebred dogs only have nongenetic issues, it would follow that purebred dogs would be the worse choice for potential dog owners looking to save on medical costs. The pre-written explanation for (B) says that the answer choice eliminates "a potential area where the costs could balance out." This refers to the fact that (B) says purebred and nonpurebred dogs are equal in nongenetic issues. In doing so, (B) rules out the possibility that nonpurebred dogs are more expensive in nongenetic issues, which could put them on an even playing field with purebred dogs who are more expensive in genetic issues. Does that make sense? Hope it helps! Please let us know if you have any other questions!