This is a weakening question, we know because the question stem says: Which one of the following, if true, most undermines the author’s prediction?
This is a nice and short stimulus; some unexpected heavy rainfall has filled reservoirs and streams, and therefore the author predicts that it won’t be necessary to ration water this summer. The assumption underlying the argument is a conditional; if the reservoirs and streams are full, then water rationing won’t be necessary. The correct answer is going to undermine this hidden premise that the reservoirs and streams being full is enough for water rationing not to be needed. Like many weakening questions, there is a lot of ways to come at this argument, and therefore POE is the best way to approach the answer choices. Let’s take a look at them:
Answer Choice (A)This is a poor answer because it relies on inductive reasoning (what happened in the past will happen in the future), and the author specifies that the reservoirs and streams being filled by heavy rainfall is a recent and unexpected phenomenon. What happened in previous years is not relevant to the support for the prediction.
Answer Choice (B) This is a very weak answer. For one, it admits that only a small part of the city’s water supply comes from this underground supply; you would expect that it would have little effect on whether water rationing will be required. All this answer does is introduce another supply in addition to the full reservoirs we’ve been told about, which would strengthen the prediction that water rationing won’t be necessary.
Correct Answer Choice (C)This answer does exactly what we identified in the stimulus; it undermines the sufficiency of full reservoirs for a lack of water rationing. If the actual transportation of the water to individuals is the issue, then a surplus of water isn’t enough to prevent water shortages among customers, and therefore it is entirely possible water rationing will be necessary even if the water supply is full.
Answer Choice (D) This answer doesn’t help us because we don’t know much about the relation of temperature to water usage. If this instead said “long-range weather forecasts predicts an extremely hot summer, which may increase water usage” then it might be helpful. But as it is stated, D fails to weaken the prediction.
Answer Choice (E) This answer is similar to A in that it relies on the inductive assumption that what happens in most years will happen in future ones. Even if this answer guaranteed that there would be less rain in the summer, for all we know the full reservoirs could supply the city for another year without any rain.
This is a weakening question: Which one of the following, if true, most seriously weakens the argument?
The first thing we learn from the stimulus is that there is this species of spider, the painted spider, and they have stickier webs than the other spiders that share their habitat. Stickier webs are better at trapping specifically flying insects, spiders hunt for food by trapping insects, and therefore the argument concludes the spider is a more successful predator than its competitors.
The overall structure of this argument is fairly simple; there is this way in which a particular kind of spider differs from others, and since this would be helpful for preying on flying insects, we conclude that in virtue of this one factor the painted spider is a better predator than its competitors. The problem with this argument is we know very little; we know very little about other possible differences between the painted spider and other spiders, about the overlap between other spiders and the painted spiders competitors, and about what portion of the prey in this habitat are specifically flying insects. The right answer is going to introduce some information that exploits one of these gaps in the argument. Let’s eliminate the answers that fail to do so:
Answer Choice (A) This addresses the issue of what portion of the prey in the habitat are specifically the flying insects which would be susceptible to the painted spider’s stickier webs. The problem is that it gives us almost no real information; “not all” could mean one single non-flying insect or almost all of the insects. Without more information, this answer is entirely compatible with both supporting this argument (a low number of non-flying insects) or weakening it (a large number of non-flying insects), and therefore does not by itself seriously weaken the argument.
Answer Choice (B) All this answer does is tell us that certain kinds of insects would be unlikely to be trapped by non-sticky webs, and therefore gives us a reason to think the painted spider might have a real advantage over other spiders. If this were a strengthening question that might be meaningful, but for us this does the opposite of what we want.
Answer Choice (C) This is just an irrelevant fact. Whether the spider paralyzes or kills its victim doesn’t bear any clear relation to the impact of its sticky webs on its success as a predator compared to its competitors.
Correct Answer Choice (D) This provides a downside to the painted spider’s stickier webs. Even if they are more efficient at trapping insects that fly into them, if they are more visible maybe much less insects fly into them, so that the painted spider is actually a much worse predator than other spiders. At the very least, this weakens the main support for the argument’s conclusion, that the painted spider’s stickier webs give it a plain and simple advantage.
Answer Choice (E) E introduces web size to equation, and does so in a really unhelpful way. If this said that the webs were significantly smaller than other spiders and therefore caught less insects, that might help us weaken the conclusion that painted spiders are better predators, but as stated this answer does nothing for us.
This is a Method of Reasoning question, and we know this because of the question stem: “The argument counters the objection by...”
The author starts out by laying out an objection to making the US school year align with Japanese/European school calendars. This objection to this proposal is that it violates a tradition that was established in the 19th century. The author then says that this objection “misses its mark,” or that their proposed reasoning that not establish support for their objection. This is our author’s main conclusion. His reasoning is that our calendar year aligned to fit harvesting time in rural areas that depended on children working. So, if we’re appealing to tradition, the tradition is actually based on economic needs and that’s what we should look to. The author is saying that the objection mistakes what the purpose of the traditions actually was.
Answer Choice (A) There is no misunderstanding about the amount of time schools have been closed.
Answer Choice (B) The stimulus is not calling into question the relevance of tradition; the author is calling into question their understanding of what said tradition means.
Correct Answer Choice (C) Note that the author’s argument takes issue with the reasoning behind the objection. This explains exactly how the author shows that the opponents of the change are misunderstanding what traditions imply for this social change.
Answer Choice (D) The author does not call into question the opponents’ genuine concern.
Answer Choice (E) The issue here is that the author isn’t saying change should be justified by tradition. If it is, however, the purpose behind the traditions the opponents put forward is not correct.
This is a Necessary Assumption question. This is a classic NA stem, and we know it’s NA because the question stem is asking for an assumption the argument depends on.
Proponents of organic farming claim something. What do they claim? Chemicals used in farming harm wildlife. Makes sense. What about it? Well, this next sentence looks like a counter-point. If we’re going to stop using chemical fertilizers and still produce the same amount of food, we’re going to have to farm more land than we currently farm. That makes sense: We don’t use chemicals for the fun of it. We use them because they dramatically increase yields. So if we stop using them, the same amount of land will produce less food. Therefore, we’ll have to farm more land to produce the same amount of food. The final line looks like the conclusion: Organic farming destroys wildlife habitat.
Well, this may seem like a somewhat reasonable argument. It may not be immediately clear to us why it isn’t valid. That’s okay though. The answer choices will feed us the prompt that will help us resolve this. We want to approach NA questions by keeping an open mind, considering what each AC suggests, and using POE to navigate through.
Answer Choice (A) This doesn’t have to be true, but it’s interesting how this is constructed. This may seem to contradict a premise, but it actually doesn’t. The first line doesn’t say that these chemicals harm wildlife. It says that organic farming proponents claim that they do. So this answer is telling us that the proponents’ claims are true. But they don’t have to be. Even if these chemicals are perfectly safe, their absence will still decrease yields and increase need for more land devoted to farming.
Answer Choice (B) This is similar to A. I’m not sure that the chemicals’ effects on wildlife, if any, actually matters. The conclusion is only addressing the effects of needing to use more land for organic farming. The chemicals don’t need to be harmful for these effects to follow from the greater land usage of organic farming. This diminishes the benefits of organic farming, but it doesn’t impact the downsides which our conclusion is solely concerned with.
Answer Choice (C) This is the same issue as A and B. Seeing a third answer choice in a row miss the point in the exact same way makes me a little cautious though. I’m not going to change course until I finish the remaining answer choices, but I am prepared to reevaluate the stimulus if this continues. The LSAT is not normally so kind as to allow us to eliminate three answer choices all for the same reason. We accept the kindness when offered, but beware test writers bearing gifts.
Answer Choice (D) This doesn’t have to be true, but it’s at least moving in a different direction from A, B, and C. And I can see why it might be attractive. If we plant different crops, maybe we can increase yields that way. By switching from a lower yield crop farmed non-organically to a higher yield crop farmed organically, maybe we can balance our yields that way without having to devote more land to farming. That makes sense and might be a possibility, but does this have to be true? No. They don’t have to be the same crop to result in lower yields. Different crops can still get us to the same result. This is an interesting suggestion, but it doesn’t check out.
Correct Answer Choice (E) Oh, this makes sense. I definitely was not going to predict this, but it totally works. I’ve been assuming that there can’t be any overlap in land use: It is used for farming or as habitat but not both. But there is nothing that says it can’t be both. If organic farming uses land in a way that preserves it as habitat, it can have multiple functions and serve as both farm land and wildlife habitat. In this scenario, greater land use would not necessarily result in the reduction of habitat. Many shade-grown coffee farming practices have this effect. The coffee plants are allowed to grow beneath and along side other trees which preserves habitat for birds.
This is a Method of Reasoning question, and we know this because of the question stem: “Judith’s reply to Anthony’s argument relies on which one of the following argumentative strategies?”
Anthony claims that using marijuana “definitely leads,” or causes, people to use heroin. His evidence is that the two tend to happen together, meaning they are correlated. He is jumping from correlation in his premise to causation in his conclusion. Our girl, Judith totally picks up on this. She’s saying this could be true, the statistics, which is his premise/evidence, does not support the causal conclusion. She then cites another correlation between water consumption and heroin use, which would lead to a berserk argument: based on Anthony’s argument for things being correlated with heroin use causes heroin use, water consumption causes heroin use. Here, she’s employing an analogy to reveal how the argument is flawed. She concludes that Anthony’s conclusion isn’t necessarily supported by his evidence/premise. Her evidence/premise is an analogy she puts forward to point out the issue in his reasoning.
Answer Choice (A) Judith never contests the factual accuracy of the statistics that Anthony offers. They could be completely accurate, but they do not support his causal conclusion.
Answer Choice (B) Judith is not undermining the credibility of his conclusion - if her first sentence, she even concedes that Anthony’s conclusion could be true. She specifically takes issue with the way he supports his conclusion.
Answer Choice (C) The example Judith cites is not promoting heroin usage; she is saying that drawing a correlation between X thing and heroin and then saying thing X causes or promotes heroin use is not true.
Correct Answer Choice (D) Judith is not questioning the premise or the conclusion, she’s simply questioning the support, or rather, the line of reasoning, between the two. By putting forward that analogy, she is showing how his line of reasoning is flawed.
Answer Choice (E) This is not good - the possibility of ever establishing a causal connection? That’s too extreme.
This is a necessary assumption question, though the question stem is quite abrupt and may present some challenges. It’s asking for an assumption, but there is no explicit indication of whether it wants a sufficient or necessary assumption. We have to really understand the nature of our assumptions to see this is necessary rather than sufficient. While it may sound obvious, sufficient assumptions are not necessary: Just because an assumption would be sufficient to validate the argument does not mean that the argument is definitely making that assumption. Necessary assumptions, on the other hard, are necessary. The argument is bound to them and cannot hold without them. Because this question stem is asking for an assumption the argument is definitely and actually making, that is how we know we are looking for a necessary assumption rather than a sufficient.
The stimulus: Well that’s interesting. Caffeine can kill certain insects, or at least their larvae. Now it looks like we have an experiment which is looking into this phenomenon. We see a certain insect die when it ingests some substance which contains caffeine, among other things. We should be drawn to the phrase “in part” because it tells us that there’s other components to whatever we’re feeding these worms. We should immediately question how we know that caffeine, and not some other component of the substance, is responsible. If this argument goes on to draw a conclusion about the effects of caffeine, it’s going to be in trouble.
And that’s exactly what it does in the last line of the sentence, which is our conclusion. The grammar is really convoluted, though, so let’s break it down to determine exactly what the conclusion is. The main body of the sentence is just “This result is evidence for the hypothesis . . .” Which hypothesis? Well, the rest of the sentence specifies which one. But the main part of the sentence is our conclusion: The result is evidence for this hypothesis.
So this doesn’t go as far as it might have. It does not say, “Therefore, caffeine totally evolved as a defense against pests.” That would have been easy to discredit. Rather, it merely says that this experiment is evidence for such a hypothesis. Is it? Well, maybe. What is evidence? Evidence doesn’t have to be conclusive. It only needs to make a proposition more likely to be true. Because there are so many other things they’re feeding to these worms, this is really weak evidence, but despite its weakness, it may nevertheless qualify as evidence. It’s hard to say for sure though. Either way, this opens up a nice big gap with lots of assumptions.
The other observation we might make from this final sentence is the reference to “non-negligible quantities.” Do tea leaves contain non-negligible quantities of caffeine? This argument does not give us an answer. And even if we assume they do, was there enough tea powder in this concoction to deliver a non-negligible dose? Maybe, maybe not. We don’t know. This new term also introduces room for assumptions.
There is a lot going on in this stimulus, and we likely have not have identified every gap. We want to proceed with a POE approach on this one and see what the answer choices might offer up for us to consider.
Answer Choice (A) Sure, maybe. This strengthens the proposition that these plants have insecticidal qualities, but what we care about is caffeine and this does not narrow down which substance in these plants is actually doing the insecticide-ing. Maybe caffeine, maybe something else. Moreover, the hypothesis is addressing caffeine as an evolutionary function, which this does not seem to touch.
Answer Choice (B) This is an interesting suggestion, but it has a problem. Does it have to be “roughly equal” to the amount in the concoction fed to the worms in the experiment? I don’t think so. It could be way higher and we would expect that to do the job.
Answer Choice (C) I can see why this might be attractive. It establishes some link between caffeine producing plants and the pests, and that does appear important to a conclusion about caffeine as an evolutionary response. What if this were not true? What if caffeine producing plants simply don’t grow wherever these pests pose a risk? “Wherever” should give us pause, though. This is a more universal statement than I’m comfortable with here. I think a 99% match would still be pretty compelling. So this gets at something close, but it misses the mark.
Answer Choice (D) Okay. So the specific worm in our experiment is a tobacco pest. What if the tobacco plant doesn’t produce caffeine? That seems like it could be a problem. How can we say caffeine evolved as a defense against these pests if these pests feed off a plant that doesn’t produce caffeine? That might seem seem to break the relevancy of the experiment with any claim about caffeine as an evolutionary mechanism. But does it? It still establishes a sensitivity to caffeine among plant pests. The fact that tobacco may not have evolved that specific defense doesn’t necessarily mean that this can’t support a hypothesis that only relies on the fact that caffeine is an effective pesticide. If D were not true, it would certainly weaken the argument. But I do not think it would destroy it.
Correct Answer Choice (E) This has to be true. No evolutionary pressure; no evolutionary response. If caffeine producing plants have literally never been preyed upon by pests which are sensitive to caffeine, there’s no way this is an evolutionary response. We do need to be a little careful though. Remember, the conclusion is very precise. We are not concluding that these plants evolved caffeine as an evolutionary defense against pests. We are concluding that the experiment with the tobacco worm is evidence that they might have. While this answer needs to be true for this to actually have been an evolutionary response, does it have to be true for this experiment to lend the hypothesis support? Yes. If the hypothesis is disproven, then there is no observation which we would say qualifies as evidence to support it. The hypothesis must remain possible for this experiment to qualify as evidence.
We know this question is a sufficient assumption question because the question stem asks which of the answer choices “enable the conclusion to be properly drawn?”
Sufficient assumption questions tend to be very formal. We’re looking for a rule that would validate the conclusion, specifically by bridging the premise and conclusion through the rule. Not only are we extrapolating the rule from our argument, but we’re plugging that rule back into the argument to make it valid. Our rule/prephrase will look like: if [premise], then [conclusion].
Our first sentence describes specific kinds of experiments and the observations from those experiments. The experiments were conducted with certain kinds of bacteria. They were placed around lots of nutrients and two things were observed: population grew (which makes sense, more nutrients = growth), and genetic mutation occurred at random. These observations are our premises.
The next sentence is the hypothesis/conclusion: based on these experiments, the author hypothesized that all genetic mutation is random. All? That’s a big jump from mutations in certain bacteria to all genetic mutations. “All genetic mutations” includes mutations that aren’t just bacteria, too. Our rule would look like: “If certain bacteria genetically mutate at random, then all genetic mutations are random.”
Remember, our paraphrase is meant to guide us through the answer choices. The answer choice may not mimic the paraphrase, but it should make the argument valid when we plug it back into the conclusion.
Correct Answer Choice (A) We know for sure that the genetic mutation did happen in our experiment, and with the dichotomy in answer choice A, we either have to accept that all mutations are random, or none are. Since we already have some random genetic mutations in bacteria in our experiments, we have to accept that all genetic mutations across lifeforms are random; accepting the latter wouldn’t make any sense and isn’t possible. In other words, if we plug this back into our argument, the conclusion is valid.
Answer Choice (B) Just because bacteria used in the experiments are common, it doesn’t mean that random genetic mutation occurring in this instance will occur in all other instances as well.
Answer Choice (C) We can’t trigger the sufficient condition in this conditional. With the information in the stimulus, we only can say that certain bacteria go through genetic mutation. This is useless.
Answer Choice (D) If we plug this back into the premises, given what we know about the massive jump the argument makes between the premise and the conclusion, this answer choice does absolutely nothing. It’s additional information that has no positive or negative bearing on the argument.
Answer Choice (E) Knowing that these bacteria are found in nature isn’t enough; we need to know about genetic mutation across life forms, not just bacteria.