This is a necessary assumption question. We see this because the argument in the stimulus depends on the assumption expressed by the correct answer choice. The assumption must be true for the argument to hold. And if the answer is not true, the conclusion will not be able to follow.
This sounds like a cool technology. The scanner can recognize patterns. Makes sense. See it once; store the data; see it again; match the new scan to the former. Simple enough. No two eyes are the same, hence its reliability because it can’t be confused by any possibility of seeing the same pattern in different eyes. The conclusion in the final sentence may initially seem reasonable enough. Isn’t this exactly what these scanners do? If you don’t see a gap here, that’s okay.
Our approach for NA questions is to keep an open mind going into the answer choices. This is particularly effective in situations like this where we may not see a gap. There is potentially a few things we might anticipate here, but we do not want to enter the AC’s searching for anything in particular. Let’s consider the Answers and let them speak to us. The correct answer choice will suggest the solution. If we’re open to it, we only need to be able to utilize the prompt to follow through and recognize the solution.
Correct Answer Choice (A) This is the right answer. To use negation: If the blood vessels could change to such an extent that the scanner can no longer match the pattern of the current scan to the previous one, then a retina scanner cannot necessarily “be used successfully to determine for any person whether it has ever scanned a retina of that person before.” If I get the right kind of eye disease, they won’t recognize me and I’m back off the grid. This would create a subset of exceptions which would not fit. Because the conclusion is universal, there are no exceptions allowed. This answer tells us that such an exception can not occur, which is necessary for the conclusion to follow.
Answer Choice (B) This is tempting because we understand that most people have two eyes and we recognize a distinction between recognizing eyes and recognizing people. If this led you astray, check the stimulus again. We’re only concluding that the retina scanner can be used to tell if it has scanned a retina of a person before. We don’t limit its methodology in how it might determine this: It could simply scan both eyes, no problem.
An even simpler reason to eliminate this answer choice, however, is that the stimulus has already told us, “no two eyes have identical patterns.” So actually, we already know that every person has different patterns of blood vessels in each eye. Those are two eyes, after all, and “no two eyes have identical patterns.” So not only is this not necessary, it contradicts the stimulus.
Answer Choice (C) We don’t care. Our conclusion is not indicating we can create a global database of scans so that we can ID anyone in the world. It only needs to be able to recognize someone it’s already scanned before. If someone isn’t already in the system, it doesn’t need to be able to recognize them per our conclusion.
Answer Choice (D) What if they’re not? Then some people would not only have different patterns of vessels but also different numbers of vessels. Would that mean the scanners couldn’t recognize people? If anything, that would give them more variation to go on. So if this isn’t true, it may even be helpful. If the negated form of this answer strengthens the argument, then this does not have to be true.
Answer Choice (E) I don’t know how this matters at all. What if there is? How does that bear on whether or not a scanner could recognize you with a second look? If you’ve been scanned by two scanners, then two scanners should be able to recognize you. No big deal. So this is not necessary.
This is a resolve reconcile explain question, indicated by the stem asking: Which one of the following, if true, most helps to reconcile the restorer’s decision with goal stated in the passage?
The stimulus tells us that the great Renaissance painter Michelangelo’s paintings in the Sistine Chapel are being restored. Awesome, who doesn’t love Michelangelo! The purpose of the restoration is to uncover the Sistine Chapel as Michelangelo originally painted it, and part of this process is removing later artists’ additions. Strangely however, the restorers have decided to leave one addition alone: that of da Volterra. We’re looking for an answer that will explain the restorers’ decision in a way that is compatible with their overall purpose of uncovering Michelangelo’s work.
Correct Answer Choice (A) Well if he stripped away all the paint then there is no Michelangelo below his addition, and therefore no benefit of removing his addition for the restorers. Their decision makes sense now!
Answer Choice (B) Cool fact but this doesn’t give us any reasons why the restorers wouldn’t remove his addition.
Answer Choice (C) I guess it might fit in more but the purpose of the restorers was to uncover Michelangelo’s original work; whether additions are stylistically similar shouldn’t affect whether they are kept in.
Answer Choice (D) The relative ranking of the different subsets of Michelangelo and Volterra’s art would have no impact on the restorers’ project. They want to uncover originals and seem to have no problem removing additions, except for Volterra’s.
Answer Choice (E) And yet the stimulus tells us they removed those other artists. That’s exactly the kind of discrepancy we want an explanation for!
This is a Necessary Assumption question because it is asking us for an answer which the argument in the stimulus depends on. This is a classic NA question stem that we want to become very familiar with and confident in easily and confidently ID’ing.
The stimulus is not particularly confusing in how it is written, but it does get into some concepts which can be a challenge.
In 1980, our Country had a higher GDP than Europe by $5,000. Great. Ten years later, that gap had grown to $6,000. At this point, we might anticipate a lot of ways this argument could go wrong. Because this is a comparative relationship between Country A and Europe, we want to recognize some of the common mistakes made with this sort of relationship. Because our points of comparison here are themselves able to change, we can’t say anything about the absolute values of either country’s per capita GDP. It might appear that Country A is wealthier than it was 10 years ago, but at this point in the argument, we can’t say this for sure. Perhaps Country A is exactly the same and Europe is $1000 poorer. Or perhaps both are poorer. Maybe Europe is $3000 poorer and Country A is merely $2000 poorer. This would give us the same change in comparative value. Because we can’t establish either country’s actual GDP to a firm number, both economic blocs could have moved in either direction on the GDP spectrum. While the argument won’t necessarily develop in a way that utilizes this, it is highly probable that it will and we should learn to recognize the nuances of this sort of relationship.
We now see the payoff in the reference to “a rising per capita GDP.” As already discussed, the information provided can not establish a rising GDP. So this sets up a huge gap in this argument. We can accept as a premise that rising GDP indicates rising standard of living, just not that a rising GDP has necessarily occurred.
The conclusion is in the second part of the final sentence: “the average standard of living in Country A must have risen . . . .”
Given the analysis here, we are probably expecting an answer which will somehow address the identified gap. There may be a lot of clever ways to do this, though, so we should evaluate each answer closely to see if it works.
Answer Choice (A) No. We don’t care about increases in population. Nothing concerning the population size needs to be true. Per capita GDP is totally unrelated to population size. Population is how many people there are. Per capita GDP is, basically, how much money those people make, on average. It can rise and fall totally independent of population. This is a popular wrong answer choice, though. If you chose this, it may be worth brushing up on some basic economic terminologies. The LSAT uses these sorts of subjects a lot, and having a basic familiarity is quite helpful on questions like this one.
Answer Choice (B) This might actually hurt this argument because it indicates to us that the stats about Europe are more flexible than this argument seems to presume. If Europe’s standard of living fell, this indicates its GDP may have fallen as well, which could explain the increase in the larger GDP gap without the need for Country A’s GDP to have risen. More to the point, though, is just that the two numbers are completely independent of one another. All we know is the difference between them. Either can rise, fall, or stay the same so long as the other moves appropriately to match it.
Answer Choice (C) This doesn’t have to be true. Europe is a big, dynamic economic bloc so it wouldn’t be surprising if this were true. But it just doesn’t matter. We’re saying Country A has had a higher GDP than Europe as a whole. Whatever is going on within Europe to create its economic situation as a whole is none of our concern.
Correct Answer Choice (D) This looks good. This means that at least some of the $1,000 increase in relative GDP came from growth in Country A. Maybe the entire $1,000, or maybe just $1, but this ensures that the GDP of Country A did, in fact, grow from 1980 to 1990.
Let’s negate to test it out. If Europe’s per capita GDP was $60,000 in 1980 and dropped by $1,001, that means its per capita GDP is $58,999 in 1990. From these numbers, we can calculate Country A’s stats. We are +$5,000 on Europe in 1980, and +$6000 in 1990. Did our GDP grow? No. It would have gone from $65,000 in 1980 to $64,999 in 1990. $64,999 is less than $65,000. So this answer has eliminated a contingency that must not occur if our conclusion is to follow.
Answer Choice (E) No, this is similar to Answer Choice C. Europe is a big, dynamic economy and we are only addressing the average of the whole. Any individual member could totally be way bigger than Country A, so long as the average of all members is less.
This is a Necessary Assumption question which we know because the question stem is asking us for an answer the argument relies on. This means the correct answer must be true if the argument is going to work, and if it isn’t true then the argument’s conclusion absolutely cannot follow.
Think about how significant a development this is in human history. Where would we be without math? And these simple counting tools are the earliest known evidence of its origins. Nice. Ok, but even though we had abstract representation of numbers as far back as 20,000 years, it was only 5,500 years ago that “systematic methods” were invented to write numbers. Okay, what about it? Well, since systematic methods only developed 5,500 years ago, conclusion: computation only became possible at that time.
I don’t really know what a “systematic method” is here, or how it differentiates from simple tally marks, but I suppose this makes sense. Ever tried to do basic division using Roman numerals? Good luck. And even Roman numerals could qualify as a systematic method since they are within our 5,500 year timeframe. Anything even worse than that and I guess I can see how calculations would be out of the question.
It’s very likely a correct answer will need to preclude more basic, non-systematic methods of representing numbers from being able to perform calculations. If I plus I equals II is a calculation, then it seems perfectly reasonable to think these 20,000 year old counting sticks could be thought of as calculators. We don’t want to commit to searching for anything in particular, and we want to stay open to suggestion of other things we may not have realized could be necessary, but it is certainly okay here if we are expecting our answer to do something in this area.
Answer Choice (A) No, we’re not interested in challenging the origins of these tools. In fact, the stimulus does not seem to entertain any possibility that these things aren’t exactly what we think they are. This certainly has nothing to do with our conclusion, in any case, and doesn’t have to be true for the conclusion to follow.
Answer Choice (B) Well I would think this would be true. I mean, we’re literally talking about rocks here. I very much doubt every last type of rock, bone, or stick was used. But even if this is almost certainly true, it doesn’t absolutely have to be true. They could’ve marked up every stick, stone, and bone on the planet and it would still have nothing to do with whether or not they were performing calculations.
Answer Choice (C) Well, yeah, but so what? They seem to date back 20,000 years. Homo sapiens evolved way longer ago than that. But, who cares? What if they do? So what? This has nothing to do with whether calculations were being performed before 5,500 years ago when “systematic methods” were invented.
Correct Answer Choice (D) Oh! This looks great. This establishes a “systematic method” of representation as a requirement for any computation. Whatever a “systematic method” is and whyever these earlier number symbols don’t qualify as systematic, we know there were no systematic methods until 5,500 years ago. This must be true for the conclusion to follow.
Answer Choice (E) We don’t care why it was invented, only when. Maybe they were invented just for the pure fun and joy of it. If so, not a problem at all.
We know this is a resolve reconcile explain question, because it asks: Which one of the following, if true, most helps to explain why the agricultural peoples of western Asia never returned to hunting and gathering?
The stimulus begins with some context; ten thousand years ago many of the communities in Western Asia switched from hunting and gathering to agriculture. Interestingly, this lead to poor diets and health issues, yet the people never returned to hunting and gathering. Our job is to explain why the communities stuck with agriculture when all we know so far is that it made their lives worse. A good answer choice will give a reason for their committal to agriculture that is compatible with the health effects mentioned in the stimulus. On to the answers:
Answer Choice (A) This doesn’t explain their committal to agriculture, it actually just makes the situation stranger by explicitly stating hunting and gathering food was still an option.
Answer Choice (B) Interesting! But this feature of both food methods doesn’t explain the committal to one over the other.
Correct Answer Choice (C) Here we go, this gives us a reason why hunting and gathering food just wasn’t going to cut it anymore, even if agriculture had negative trade offs. If one option isn’t going to work anymore, then sticking to the other makes sense.
Answer Choice (D) This tells us the phenomenon was widespread, but doesn’t provide an explanation for why it occurred in the first place.
Answer Choice (E) This just seems like another downside to agriculture, which makes the committal of the communities even less intelligible.
Here we have a resolve reconcile explain question, since it asks: Which one of the following, if true, most helps to resolve the apparent discrepancy?
Our stimulus begins by telling us that Mr. Young has the highest rate of unsuccessful collections at a collection agency. However, he is the best bill collector the agency has. The discrepancy is that we would expect a good bill collector to have less unsuccessful collections. We want to resolve this discrepancy by finding an answer choice which explains why Mr. Young might have a lot of unsuccessful collections in a way that is compatible with him being the best bill collector. Let’s see what we get!
Correct Answer Choice (A) This does exactly what we want! It would make sense that the hardest cases go to the best bill collector, and that the difficulty of these cases would lead to more unsuccessful collections.
Answer Choice (B) That’s very nice of the other bill collectors, but their opinions don’t do anything to explain why he has so many unsuccessful cases!
Answer Choice (C) Interesting! But again, his rate of collections remaining constant doesn’t explain a high rate of failed collections compared to others.
Answer Choice (D) Save it for his biography, this does nothing to help us!
Answer Choice (E) This just gives us another reason why we’d expect him to have a lower rate of unsuccessful collections compared to his juniors.
This is a weakening question, as the question stem asks: Which one of the following, if true, casts the most doubt on the accuracy of the above conclusion?
This stimulus is placed in quotes without an identified speaker, but this doesn’t really matter beyond allowing some of the referential phrasing such as this company. It begins with the context that the speaker’s company will not be training more pilots, as they have a waitlist of 400 trained pilots. Alright, that kind of makes sense. This decision is then supported by an argument.
The argument begins with the premise that the five other major companies have roughly ~ 400 pilots as well. The stimulus continues with another premise with the support indicator since, stating that each company is going to only need roughly ~100 pilots. From these two premises about the company waitlists and personnel needs, the author concludes that there will be no shortage of personnel. The assumption this argument depends on is that the individuals waitlisted for each company are distinct. Since each company requires about ~100 people and there are 5 companies, around ~500 pilots are needed by the major companies. For the argument to conclude that there are enough trained pilots to avoid a shortage, it must assume that it isn’t the same 400 pilots waitlisted for each company, as in that case there would actually already be a shortage brewing since there are ~100 less pilots than needed. An answer which picks up on this assumption and contradicts it will be an excellent weakening answer. Let’s see what we get:
Correct Answer Choice (A) This does exactly what we identified with our pre-phrase, it directly contradicts the arguments assumption that there isn’t significant overlap between the waitlists.
Answer Choice (B) Our author’s argument is specifically about the forseeable future, the argument’s conclusion is not about whether or not training will be needed in the long run.
Answer Choice (C) Ok? Our author’s conclusion is a prediction that there will be no shortage in the foreseeable future; whether or not there will be an age gap does nothing to weaken the argument.
Answer Choice (D) If anything this strengthens the argument by supporting the accuracy of the author’s claims.
Answer Choice (E) If other companies are training more pilots, that strengthens the author’s prediction that there won’t be a shortage.
This is a resolve reconcile explain question, though it may be difficult to identify. The phenomenon we are trying to explain is how the statistic could be accurate if the conclusion isn’t, i.e. how could emergency room visits grow if heroin use remained constant or declined. The question stem asks us: Which one of the following, if true, would account for the statistic above without supporting the author’s conclusion?
The statistic mentioned in the stem is that the amount of emergency room visits by heroin users increased by 20% during the 80s. The author concludes that this was a result of an increase in the use of heroin, but we want to explain why the phenomenon identified by the statistic occurred without supporting this conclusion, so our hypothesis can’t involve an increase in heroin use. We are therefore looking for an alternative hypothesis. Let’s see what we get in the answer choices.
Correct Answer Choice (A) Bingo! This answer gives us a reason for why more heroin users would end up in the hospital even if there wasn’t an increase in heroin use, namely, increased violence from the drug trade.
Answer Choice (B) If it reduced the risk of infection, we would expect a decrease in the number of hospital visits.
Answer Choice (C) Interesting, but this does nothing to explain why there was such an increase in the first place.
Answer Choice (D) Remember, we don’t want to support the conclusion that heroin use increased!
Answer Choice (E) This gives us a more detailed explanation of what specific issues caused heroin users to go to the emergency room, but not why the amount of them who did so increased. This is a more complete description of the phenomenon, not a hypothesis for why it occurred.
This is a resolve reconcile explain question, as the question stem asks: Which one of the following, if true, is most helpful in resolving the apparent paradox?
The stimulus opens with a study by the government, which discovered that consumers who opted for bottled water were receiving a more expensive and dangerous product than the public water supply. Seems like a bad deal! Weirdly, even though the study received a lot of attention, people have been buying even more bottled water. The question stem asks us to resolve a paradox; in this case the paradox is that the opposite outcome we would have expected followed the release of the study. Our job is to select the answer choice which provides the best hypothesis for why this weird result occurred. Let’s see what we get:
Answer Choice (A) This seems like another reason for why people should be choosing drinking water instead of bottled water, and does nothing to explain the fact that they aren’t.
Answer Choice (B) This eliminates a potential difference between the two water sources which might explain the consumer preference, and therefore makes the result even weirder without explaining it at all.
Correct Answer Choice (C) This answer explains the paradox by differentiating between subsets of bottled water. Although many kinds of bottled water were less safe than public water, the increase in sales actually came from specifically the brands that were identified as superior to public water in the report.
Answer Choice (D) This makes it slightly less weird, but still does nothing to explain why there was an increase at all.
Answer Choice (E) We are talking about bottled water, not food, and regardless this suggests that consumers do care about what the government says, which makes their apparent disregard of the study stranger.
This is a resolve, reconcile, or explain question, since the stem asks us: Which one of the following, if true, most helps to explain the study’s finding?
The stimulus begins with a yearlong study, in which half of the participants were given a kit to test their cholesterol. The result of the study was that the participants with testing kits reduced, on average, their cholesterol levels 15% more than the no-kit group. Interesting! So being able to test your cholesterol levels seems to help reduce them. The stimulus finishes with two final tidbits; the participants were (i) randomly selected, and specifically from (ii) those who have very high cholesterol levels. Our job here is to explain why having access to testing kits would enable high-cholesterol individuals to reduce their cholesterol more. We are looking for a powerful hypothesis for the difference between the kit-havers and kit-not-havers which relies on as few assumptions as possible. Let’s see what we get:
Answer Choice (A) All participants had high cholesterol, and it’s unclear how accuracy would even affect the amount participants would reduce their cholesterol.
Answer Choice (B) This would make things even more confusing, because they would have lowered their cholesterol by more while avoiding cholesterol-lowering food!
Answer Choice (C) Ok? This gives us no reason for why the tests themselves helped people lower their cholesterol levels.
Answer Choice (D) Our phenomenon is a difference between the kit-havers and kit-not-havers; this information does nothing to explain that difference among the subsets.
Correct Answer Choice (E) If using the kit reinforced cholesterol reduction efforts, then it would make sense why kit-havers reduced their cholesterol by a greater amount!