Summarize Argument
The author concludes that there’s not much justification for health warnings that urge removal of all bats that live in buildings where people work/live. This is based on the fact that bats are shy animals that rarely bite, and the fact that the overwhelming majority of bats don’t have rabies.
Notable Assumptions
The author assumes that the risk of being bitten by bats, whether they have rabies or not, does not provide significant justification for removing bats from all buildings where people work/live. The author assumes that there aren’t significant reasons we should remove all bats from the buildings, despite the unlikelihood of being bitten by a rabid bat.
A
A rabid bat is much more likely to infect another bat than to infect any other type of animal.
This suggests bats pose more risk to other bats than to other animals, such as humans. This is consistent with the author’s position, which is that we don’t have much justification to remove all bats from buildings with people.
B
Rabid bats are less mobile than other bats but are much more aggressive.
(B) gives us reason to think that rabid bats are likely to bite more often than other bats, which means that the general tendency (”rarely bite”) pointed out by the author does not apply to rabid bats. This undermines the support provided by that premise.
C
Most animals that carry rabies are animals of species that, under normal conditions, very rarely bite people.
This has no clear impact. Most animals with rabies could be raccoons, weasels, rats, etc. This doesn’t suggest that rabid bats are more likely to bite people than normal bats, or that there’s something about bats that should justify removing them from buildings.
D
The bat species with the highest incidence of rabies do not live in buildings.
If anything, this might support the author’s position by eliminating the possibility that the most rabid bats live in buildings, which might otherwise give us a reason to remove bats from buildings.
E
People are more likely to be aware of having been bitten by a bat if they were bitten by the bat inside a building.
This has no clear impact. If people are more likely to be aware of being bitten by a bat in a building, that doesn’t suggest we might want to remove bats from buildings.
Monarch butterflies must contend with single-celled parasites that can cause deformities that interfere with their flight. In populations of monarch butterflies that have not migrated, as many as 95 percent are heavily infected by the parasites, while less than 15 percent of those in migrating populations are infected. This shows that migrating allows monarch butterflies to avoid these parasites.
Summarize Argument: Phenomenon-Hypothesis
The author hypothesizes that migration allows monarchs to avoid the parasites. She supports this by saying that up to 95% of non-migrating monarch populations are infected, while less than 15% of migrating populations are infected. She also says the parasites can interfere with monarchs’ flight.
Identify and Describe Flaw
This is the cookie-cutter flaw of assuming that correlation proves causation. The author notes a correlation between migration and lower infection percentages and then concludes that migration causes monarchs to avoid infection. Her reasoning is flawed because she overlooks two key alternative hypotheses:
(1) The causal relationship could be reversed—maybe parasitic infections prevent monarchs from migrating, not the other way around.
(2) Another factor might cause certain populations to not migrate and to be more vulnerable to parasites.
A
monarch butterflies are unable to detect which areas are free from parasites
Migrating monarchs have a lower percentage of infections, but it doesn’t matter whether they can detect which areas are free from parasites. Even if the author did address this, it wouldn’t impact her conclusion that migration allows these monarchs to avoid parasites.
B
long migrations are no better protection from parasites than are short migrations
The author just concludes that migration allows monarchs to avoid the parasites; she never claims that long migrations are better than short ones. Even if long and short migrations are equally effective, this wouldn’t impact her conclusion.
C
populations of monarch butterflies that have not migrated are much larger than migrating populations
The author addresses the percentage of monarchs infected, not the number. Even if there are more non-migrating monarchs, it doesn't change the fact that they have a higher percentage of infections. The question of what causes this higher percentage still remains.
D
monarch butterflies infected with parasites are typically unable to migrate
The author overlooks the possibility that the causal relationship is reversed. Maybe the parasites cause monarchs not to migrate, rather than the other way around. After all, the author does say that the parasites can interfere with the monarchs’ flight.
E
populations of monarch butterflies tend not to migrate if they have stable food sources
Even if monarchs with stable food sources tend not to migrate, this doesn’t change the fact that these non-migrating populations have a higher percentage of infections. It also doesn’t affect the conclusion that migration helps the migrating monarchs to avoid the parasites.
Summarize Argument
The Psychologist concludes that thinking can occur without language. Why? Because infants with no knowledge of language can spot irregularities in pictures. To do this, the infants probably compare the picture with an internal representation of what is typical, and so a thought of what is typical must exist in the infants’ minds.
Identify Argument Part
The statement in the last sentence is a sub-conclusion used to support the Psychologist’s main conclusion.
A
It is a conclusion drawn and used in turn as a premise to support a more general conclusion.
The statement is a sub-conclusion used as support for the Psychologist’s general conclusion: thinking can occur without language.
B
It is attributed to certain researchers as the main conclusion of their reasoning.
The statement is not the Psychologist’s main conclusion.
C
It is the main point of the psychologist’s argument.
The statement is not the Psychologist’s main conclusion.
D
It is used to refute the claim that infants have no knowledge of language.
The claim that infants have no knowledge of language is never refuted.
E
It states the hypothesis to be explained by the psychologist’s argument.
The statement is not a hypothesis.
Summary
Any time a bird flies, powerful forces converge on its shoulder joints. If they are flying, the bird’s wings must be kept stable during flight. If their wings are stable, something needs to balance these powerful forces. The only structure in birds that can balance these forces is a ligament that connects the wings to the shoulder joint. So that ligament must be (the correct answer is the conclusion).
Strongly Supported Conclusions
The ligament is how birds stabilize their wings while flying.
Bird Flying -> wings stable -> balance powerful forces
Bird Flying -> wings stable -> balance powerful forces
A
the only structure that is indispensable to bird flight
The stimulus gives no indication that this ligament is the *only* structure necessary for bird flight. This is too strong to support and does not follow logically from the argument.
B
the reason that a bird’s wings must be kept stable during flight
The stimulus does not explain exactly *why* the bird’s wings must be kept stable. The stimulus is primarily concerned with the importance of stability, but not the reasons for it.
C
the sole connection between the wing and the shoulder joint
The stimulus says that the ligament is the only structure *capable of balancing* the wings, not that it is the sole connection. This is too strong to support.
D
the source of the powerful forces that converge on the shoulder joint
The stimulus does not explain where these powerful forces come from. The stimulus only says that these ligaments *balance* the powerful sources.
E
the means by which a bird stabilizes its wings during flight
The stimulus says that *the only structure* capable of balancing the wings is this ligament. Thus, the ligament must keep its wings stable because nothing else can.
"Surprising" Phenomenon
Why have auto thefts dropped dramatically in cities where car owners have the antitheft device installed, even though only a small % of car owners in those cities have installed the device?
Objective
The correct answer should help explain how only a small proportion of cars being equipped with antitheft devices can still lead to a significant decrease in the car theft rate.
A
Car thieves will tend to be less cautious if they are unaware that a car they have stolen contains a homing beacon.
But there’s still only a small % of cars with the device. Car thieves might be less cautious if they don’t know about these devices, which might mean these thieves get caught, but how could this dramatically decrease overall theft rates?
B
Typically, the number of cars stolen in cities where the homing beacons are in use was below average before the device was used.
We’re trying to explain how theft rates could have decreased. Whether theft rates started below, at, or above the average theft rates for cities doesn’t explain how those rates could have declined dramatically.
C
Before the invention of the homing beacon, automobile thieves who stole cars containing antitheft devices were rarely apprehended.
Even if we interpret this answer as suggesting thieves today are more frequently apprehended, wouldn’t we expect only a small proportion of thieves to be caught, since the device is installed in only a small proportion of cars? How could this significantly decrease cars stolen?
D
A large proportion of stolen cars are stolen from people who do not live in the cities where they are stolen.
We know only a small % of cars have the device installed in the relevant cities. Whether thieves live in other cities doesn’t affect our expectation that a small % of cars with the device should have only a small impact on overall theft rate.
E
In most cities the majority of car thefts are committed by a few very experienced car thieves.
If only a few car thieves are responsible for a large portion of car thefts, catching only a few car thieves can lead to a dramatic decline in thefts. This is how the devices could decrease thefts significantly despite being in only a small % of cars.
Summarize Argument
The author concludes that cash gifts of gift cards are more highly valued by recipients than are gifts chosen for them by others. This is based on a study in which people were asked how much they would have been willing to pay for gifts chosen for them by others. People responded with amounts that were, on average, two-thirds the actual price of the gifts.
Notable Assumptions
The author assumes that the amount people state for how much they would have been willing to pay for a gift is an accurate measure of how much they value the gift.
A
The rate at which gifts are returned to retailers has been steadily increasing since the rate was first measured.
The increasing return rate has no clear impact on how much people value gifts chosen by others. If (A) does anything, it might support the idea that people prefer the cash equivalent of a gift over the gift.
B
Gifts of cash and gift cards currently represent only about 14 percent of all gift giving.
How often people give gifts of cash or gift cards has no clear impact on whether people value the cash equivalent more than a gift chosen by others. Perhaps people tend not to give cash or gift cards because it’s perceived as worse than giving someone else a gift?
C
People in the study would have been willing to pay more for gifts chosen for them by close friends and relatives than for gifts chosen for them by others.
This compares gifts chosen by close friends/relatives to gifts chosen by other kinds of people. But this comparison, which is between subsets of the “gifts chosen by others,” doesn’t affect the comparison between gifts chosen by others and cash/gift cards.
D
People are unwilling to sell gifts chosen for them by others unless offered about one and a half times the gift’s actual price.
This presents a competing method of determining how much people value a gift, which produces a conflicting result. If people are unwilling to sell a gift unless offered more than its actual price, that arguably suggests people value gifts more than the cash equivalent.
E
Most retailers require receipts before people can return gifts for refund or exchange.
Whether retailers require receipts has no clear impact on the comparison between gifts and cash/gift cards.
Summary
Creating secure passwords for confidential computer files is difficult. Users prefer passwords that are easy to remember. Unfortunately, these passwords are the easiest to guess for an outsider. Random configurations of letters and numbers are the hardest for an outsider to guess, but also the easiest for a legitimate user to forget. Furthermore, passwords that are very difficult to remember are generally written down, and hence pose the greatest security threat of all.
Notable Valid Inferences
Passwords that are easy for an outsider to guess have less of a security threat than passwords that are very difficult to remember.
A
Computer users should not write down their passwords even if the passwords are hard to remember.
Could be false. The stimulus does not state a value judgement about what users should not do. We know that written passwords pose the greatest security threat, but it is possible there are other reasons to write passwords that outweigh these risks.
B
It is expensive to have system administrators constantly resetting forgetful users’ passwords.
Could be false. The stimulus tells us that users who forget their passwords use up the administrator’s time, but we don’t have any information about how much this costs. It is possible that a system administrator’s time is not expensive.
C
Passwords that are very easy to guess pose less of a security threat than passwords that are very difficult to remember.
Must be true. The stimulus tells us that very difficult passwords to remember are usually written down, a practice that poses the greatest security threat. If this practice poses the greatest threat, then the threat associated with passwords that are easy to guess is less.
D
Passwords that are random configurations of letters and numbers are the least likely to result in security breaches.
Could be false. The stimulus tells us that these passwords are the easiest for legitimate users to forget. If they are the hardest to remember, then they may usually be written down and therefore pose the greatest security threat.
E
The easier a password is to remember, the more secure the computer account.
Could be false. The stimulus does not describe a correlation between security risk and the ease of remembering a password. It is possible that there is a point where the security level maximizes even though the password could change to become easier to remember.