DAILY EXERCISES: CR

31. Which of the following most logically completes the argument?

Ferber's syndrome, a viral disease that frequently affects cattle, is transmitted to these animals through infected

feed. Even though chickens commercially raised for meat are often fed the type of feed identified as the source

of infection in cattle, Ferber's syndrome is only rarely observed in chickens. This fact, however, does not

indicate that most chickens are immune to the virus that causes Ferber's syndrome, since .

(A) chickens and cattle are not the only kinds of farm animal that are typically fed the type of feed liable to be

contaminated with the virus that causes Ferber's syndrome

(B) Ferber's syndrome has been found in animals that have not been fed the type of feed liable to be

contaminated with the virus that can cause the disease

by exposure to a closely related infectious organism

(D) chickens and cattle take more than a year to show symptoms of Ferber's syndrome, and chickens

commercially raised for meat, unlike cattle, are generally brought to market during the first year of life

(E) the type of feed liable to be infected with the virus that causes Ferber's syndrome generally constitutes a

larger proportion of the diet of commercially raised chickens than of commercially raised cattle

Argument Construction

Situation Certain feed given to cows and to chickens commercially raised for meat is infected with

the virus that causes Ferber's syndrome. Cows are frequently affected by this disease,

while it is rarely observed in chickens. But (for a reason the argument omits) this does

not suggest that chickens are immune to the virus.

Reasoning What point would most logically complete the argument? How could it be the case

that chickens are infected, yet Ferber's syndrome is only rarely observed in them? The

important point here is that Ferber's syndrome is not observed in chickens. A disease is

usually observed to be present on the basis of its symptoms. Those symptoms might not

be present, or might not yet be present, in chickens that are infected with the virus. If the

chickens were used for meat before they began showing symptoms, then they would not

be observed to have Ferber's syndrome, but this would not indicate that they were

immune to the virus.

A That other animals are fed the potentially contaminated feed is not relevant to the question of

whether chickens are immune to the virus.

B The idea that there could be a source of the virus other than contaminated feed does not have any

bearing on whether chickens are immune to the virus.

C The idea that there is a way for animals to acquire a resistance to the virus that causes Ferber's

syndrome suggests that some animals, possibly chickens, might be immune to the virus. This is

the opposite of what the argument is trying to establish.

D Correct. This statement properly identifies a point that logically completes the argument: It

provides a reason why infected chickens would fail to show symptoms of Ferber's syndrome.

E If chickens' diets contain proportionally more of the potentially infected feed than cattle's diets

do, it is even more surprising that Ferber's syndrome is not observed in chickens—far from

providing a reason not to conclude that chickens are immune to the virus; this makes it seem

even more likely that they are immune.

The correct answer is D.

32. Last year the rate of inflation was 1.2 percent, but for the current year it has been 4 percent. We can conclude

that inflation is on an upward trend and the rate will be still higher next year.

Which of the following, if true, most seriously weakens the conclusion above?

(A) The inflation ﬁgures were computed on the basis of a representative sample of economic data rather than

all of the available data.

(B) Last year a dip in oil prices brought inflation temporarily below its recent stable annual level of 4 percent.

or above, these pay raises constitute a force causing further inflation.

(D) The 1.2 percent rate of inflation last year represented a 10-year low.

(E) Government intervention cannot affect the rate of inflation to any signiﬁcant degree.

Argument Evaluation

Situation The rate of inflation was 1.2 percent last year but is 4 percent in the current year. It is

therefore expected to rise above 4 percent next year.

Reasoning What point most weakens this conclusion? The conclusion is based on an upward trend that

is derived from data for two years. Data from only two years provide rather weak

evidence of a trend. Additional evidence that provides a context for the annual inflation

rates during the most recent two-year period will promote a more solid evaluation of this

prediction of next year's inflation rate. If inflation has recently been stable at 4 percent,

and the temporary drop the previous year is accounted for by lower oil prices, then the

basis for the prediction seems quite weak.

A As long as the sample was representative, the figures should be accurate. This point does not

weaken the conclusion.

B Correct. This statement suggests that the 1.2 percent inflation rate is an unusual occurrence in

recent years. Especially because the dip below the stable 4 percent rate was temporary, this

unusual occurrence cannot be used as the basis for predicting a trend.

C This statement explains one process by which inflation increases and tends to support the

conclusion that inflation will continue to rise.

D This information implies, for example, that two years ago, the inflation rate was higher than

1.2 percent. This raises the possibility (without stating it) that last year and the year preceding

mark a trend of declining inflation (and that the current year's 4 percent is an aberration).

However, if the inflation rate two years ago was only slightly higher than 1.2 percent (for

example, 1.25 percent), then it would be difficult to regard these two numbers as signaling a

trend of declining inflation. We do not have enough information here to regard this as a

significant weakener. The information is sufficient to justify a little doubt about the argument's

conclusion—but not at all specific enough to undermine the argument's conclusion as much as

does answer choice (B).

E The failure of government intervention to affect the rate of inflation could be seen to support, not

weaken, the conclusion.

The correct answer is B.

33. Which of the following most logically completes the argument below?

Although the number of large artificial satellites orbiting the Earth is small compared to the number of small

pieces of debris in orbit, the large satellites interfere more seriously with telescope observations because of the

strong reflections they produce. Because many of those large satellites have ceased to function, the proposal

has recently been made to eliminate interference from nonfunctioning satellites by exploding them in space.

This proposal, however, is ill conceived, since .

(A) many nonfunctioning satellites remain in orbit for years

(B) for satellites that have ceased to function, repairing them while they are in orbit would be prohibitively

expensive

(D) the only way to make telescope observations without any interference from debris in orbit is to use

telescopes launched into extremely high orbits around the Earth

(E) a greatly increased number of small particles in Earth's orbit would result in a blanket of reflections that

would make certain valuable telescope observations impossible

Evaluation of a Plan

Situation Many large artificial satellites orbiting earth no longer function. Reflections from these

satellites interfere with telescope observations. A proposal has been made to eliminate

this interference by exploding these satellites in space.

Reasoning Why is the proposal ill conceived? If exploding the large artificial satellites—thereby

creating a large amount of debris—would result in an increase in interference with

telescope observation, the proposal would be self-defeating, and therefore would be ill

conceived.

A The fact that many nonfunctioning satellites remain in orbit for years would seem to make the

proposal more attractive. If large nonfunctioning artificial satellites generally do not remain in

orbit for years—e.g., if they fall out of orbit—then there might be no need to explode the satellites.

Therefore this statement is not correct.

B This statement, too, makes the proposal more attractive—the opposite of what is called for. If

nonfunctioning satellites cannot be repaired, then that eliminates one possible reason for not

blowing them up.

C The fact that there are no known instances of intentional explosions of satellites does not show that

the plan is ill conceived. At most this might suggest that the consequences of such an explosion

are not well understood, but even that is not very strongly suggested. For instance, if large artificial

satellites have accidentally blown up, scientists may have studied the results and have good reason

to believe that no ill-effects will result from exploding the satellites.

D This is not a cogent reason for thinking the proposal to be ill conceived. Even if the proposal

would not eliminate all interference with ground based telescopes, it might still greatly reduce

interference.

E Correct. If exploding large nonfunctioning satellites would lead to more interference, then we

have a reason to think that the proposal is ill conceived.

The correct answer is E.

34. Thyrian lawmaker: Thyria's Cheese Importation Board inspects all cheese shipments to Thyria and rejects

shipments not meeting specified standards. Yet only 1 percent is ever rejected. Therefore, since the health

consequences and associated economic costs of not rejecting that 1 percent are negligible, whereas the

board's operating costs are considerable, for economic reasons alone the board should be disbanded.

Consultant: I disagree. The threat of having their shipments rejected deters many cheese exporters from

shipping substandard product.

The consultant responds to the lawmaker's argument by

(A) rejecting the lawmaker's argument while proposing that the standards according to which the board

inspects imported cheese should be raised

(B) providing evidence that the lawmaker's argument has significantly overestimated the cost of maintaining

the board

(D) pointing out a benefit of maintaining the board, which the lawmaker's argument has failed to consider

(E) shifting the discussion from the argument at hand to an attack on the integrity of the cheese inspectors

Argument Construction

Situation The Thyrian lawmaker argues that the Cheese Importation Board should be disbanded,

because its operating costs are high and it rejects only a small percentage of the cheese it

inspects. The consultant disagrees, pointing out that the board's inspections deter those

who export cheese to Thyria from shipping substandard cheese.

Reasoning What strategy does the consultant use in the counterargument? The consultant indicates to the

lawmaker that there is a reason to retain the board that the lawmaker has not considered.

The benefit the board provides is not that it identifies a great deal of substandard cheese

and rejects it (thus keeping the public healthy), but that the possibility that their cheese

could be found substandard is what keeps exporters from attempting to export lowquality

cheese to Thyria.

A The consultant does reject the lawmaker's argument, but the consultant does not propose higher

standards. Indeed, in suggesting that the board should be retained, the consultant implies that

the board's standards are appropriate.

B The consultant does not provide any evidence related to the board's cost.

C The only point the lawmaker raises that is not strictly economic is about the health consequences

of disbanding the board, but the consultant does not address this point at all.

D Correct. This statement properly identifies the strategy the consultant employs in his or her

counterargument. The consultant points out that the board provides a significant benefit that the

lawmaker did not consider.

E The consultant does not attack the integrity of the cheese inspectors; to the contrary, the

consultant says that their inspections deter the cheese exporters from shipping substandard

cheese.

The correct answer is D.

35. Which of the following best completes the passage below?

The computer industry's estimate that it loses millions of dollars when users illegally copy programs without

paying for them is greatly exaggerated. Most of the illegal copying is done by people with no serious interest in

the programs. Thus, the loss to the industry is quite small, because .

(A) many users who illegally copy programs never ﬁnd any use for them

(B) most people who illegally copy programs would not purchase them even if purchasing them were the only

way to obtain them

ﬁnancial difﬁculties

(D) the total market value of all illegal copies is low in comparison to the total revenue of the computer

industry

(E) the number of programs that are frequently copied illegally is low in comparison to the number of

programs available for sale

Argument Construction

Situation The computer industry's estimate of its losses due to illegally copied programs is

exaggerated—and actually quite small—because most of the illegal copying is done by

people who are not greatly interested in the programs.

Reasoning Why would the loss to the industry be said to be small? The industry's loss due to illegal

copying of programs must be evaluated in terms of the sales lost; the actual loss to the

industry is directly related to the legitimate sales opportunities that have been lost.

Would the people illegally copying the programs buy them if they could not otherwise

obtain them? If it were true that most of them have no serious interest in the programs, they

would be unlikely to purchase them. In this case, few sales would be lost and the loss to

the industry could be considered small.

A What users do (or do not do) with programs once they have them does not help to show that the

loss to the industry is small.

B Correct. This information provides a reason supporting the claim that the industry has not lost

potential sales.

C The greater financial difficulties of the industry do not help to show that the loss incurred because

of the illegally copied programs is small.

D This comparison is faulty: The loss is not being considered in the context of total industry

revenues but in the context of total sales of programs.

E This information does not provide a good reason for the claim that the loss to the industry is

small. Even if the number of programs frequently copied is low, the number of copies made from

each program might be huge (for the most popular programs).

The correct answer is B.

36. The growing popularity of computer-based activities was widely expected to result in a decline in television

viewing, since it had been assumed that people lack sufficient free time to maintain current television-viewing

levels while spending increasing amounts of free time on the computer. That assumption, however, is evidently

false: In a recent mail survey concerning media use, a very large majority of respondents who report increasing

time spent per week using computers report no change in time spent watching television.

Which of the following would it be most useful to determine in order to evaluate the argument?

(A) Whether a large majority of the survey respondents reported watching television regularly

(B) Whether the amount of time spent watching television is declining among people who report that they

rarely or never use computers

per week using computers increases

(D) Whether a large majority of the computer owners in the survey reported spending increasing amounts of

time per week using computers

(E) Whether the survey respondents' reports of time spent using computers included time spent using

computers at work

Argument Evaluation

Situation The argument is intended to debunk the assumption that people lack sufficient free time

to maintain television-viewing levels while spending increasing amounts of free time on

the computer. To do so, it cites a survey of media use in which a large majority of

respondents who spend increasing amounts of time using computers also claim to have

not altered the amount of time they spend watching television.

Reasoning What would it be most useful to know in order to evaluate the argument? The argument uses

the survey results to claim that people have enough free time to both maintain their

television viewing levels and spend increasing amounts of free time on the computer. But

the survey, as reported here, did not address whether people are spending their free time

on the computer; the respondents reported increasing time spent per week using

computers. Since the argument is about free time, it is important to know whether this is

actually what the respondents were reporting.

A The argument is concerned with the change in the amount of television watched by those whose

computer use increased, so whether the survey's respondents reported watching television

regularly is irrelevant.

B The argument is concerned with the change in the amount of television watched by those whose

computer use has increased, so it does not matter whether the amount of time spent watching

television among people who do not use computers is declining, remaining the same, or

increasing.

C The argument is concerned with the amount of television watched by those whose computer use

has increased, not the type of television programs such a person does or does not watch.

D The argument here is concerned with people who report spending increasing amounts of time on

the computer; what computer owners do is a separate question.

E Correct. This statement properly identifies something that would be useful to know in evaluating

the argument: whether the survey data included time spent using computers at work—if it did,

this would make the data misleading as evidence for the argument's conclusion.

The correct answer is E.

37. In the last decade there has been a signiﬁcant decrease in coffee consumption. During this same time, there

has been increasing publicity about the adverse long-term effects on health of the caffeine in coffee.

Therefore, the decrease in coffee consumption must have been caused by consumers' awareness of the

harmful effects of caffeine.

Which of the following, if true, most seriously calls into question the explanation above?

(A) On average, people consume 30 percent less coffee today than they did 10 years ago.

(B) Heavy coffee drinkers may have mild withdrawal symptoms, such as headaches, for a day or so after

signiﬁcantly decreasing their coffee consumption.

(D) The consumption of fruit juices and caffeine-free herbal teas has increased over the past decade.

(E) Coffee prices increased steadily in the past decade because of unusually severe frosts in coffee-growing

nations.

Argument Evaluation

Situation The decrease in coffee consumption in the last decade can be explained by consumers'

increased awareness of the detrimental effects of the caffeine in coffee.

Reasoning What point weakens this explanation? A conclusion offering an explanation for some

occurrence may be weakened when another explanation at least as compelling as the

original is offered. Coffee consumption may have decreased over the decade for some

reason other than consumers' awareness of the adverse health effects of caffeine. If the

price of coffee has increased in the same period that consumption has decreased, then

the decrease may well be the result of consumers' attention to price rather than their

attention to health. Higher prices would offer a good alternative explanation that would

weaken the original explanation.

A This point merely tells us how much coffee consumption has decreased; it does not make the

explanation offered in the conclusion any less likely to be correct.

B Withdrawal symptoms would occur only after decreased consumption has occurred and so

cannot explain why the decrease occurred.

C Suppose that the specialty coffees that had their sales hold steady were all caffeine-free coffees;

note that nothing rules this out. If this were the case, the explanation would remain plausible.

D An increase in the consumption of these drinks could plausibly be the result of some coffee

drinkers switching to these drinks to avoid the negative effects of caffeine.

E Correct. This statement properly identifies a plausible alternative explanation and therefore

undermines the given explanation.

The correct answer is E.

38. Which of the following best completes the passage below?

When the products of several competing suppliers are perceived by consumers to be essentially the same,

classical economics predicts that price competition will reduce prices to the same minimal levels and all

suppliers' proﬁts to the same minimal levels. Therefore, if classical economics is true, and given suppliers'

desire to make as much proﬁt as possible, it should be expected that .

(A) in a crowded market widely differing prices will be charged for products that are essentially the same as

each other

(B) as a market becomes less crowded as suppliers leave, the proﬁts of the remaining suppliers will tend to

decrease

its competitors' products.

(D) when consumers are unable to distinguish the products in a crowded market, consumers will judge that

the higher-priced products are of higher quality

(E) suppliers in crowded markets will have more incentive to reduce prices and thus increase sales than to

introduce innovations that would distinguish their product from their competitors' products

Argument Construction

Situation Classical economics holds that prices and profits are minimal when consumers perceive

the products of competing suppliers to be the same.

Reasoning According to classical economics, what strategy are suppliers most likely to use to maximize profits

in such a situation? The given information states that the force driving prices and profits

down in this case is the consumers' perception that the competing products are essentially

the same. It is reasonable to assume that, with prices already at minimal levels, it is not

possible to lower them any more. What can be done? The suppliers' most likely strategy

would then be to change the consumers' perception of their products. It can be expected

that an individual supplier would try to convince consumers that its product greatly

differs from (and is certainly preferable to) the products of its competitors.

A According to classical economics, prices will be reduced by competition to the same minimal levels

as long as the products are perceived by consumers to be essentially the same, and nothing indicates

that they will not be; therefore there is no reason to believe that prices will differ widely.

B The passage discusses the conditions of a crowded market, not a market that is becoming less

crowded.

C Correct. This statement properly suggests that the most likely strategy for any one supplier in

a crowded market is convincing consumers that its product is very different from those of its

competitors.

D According to classical economics, prices will be reduced to the same minimal levels when consumers

are unable to distinguish among the products; therefore none of the products will be priced

higher than any others.

E The passage gives no indication of what classical economics says about the attractiveness to

suppliers of reducing prices versus introducing innovations.

The correct answer is C.

39. Which of the following most logically completes the argument?

Sviatovin is a medieval Moringian text whose author and exact date of composition are unknown. However, the

events in the life of Prince Sviatov that the text describes occurred in 1165, and in the diagram of Sviatov's

family that accompanies the text his father, who died in 1167, is identified as still living. Thus Sviatovin must

have been written between 1165 and 1167, assuming that .

(A) the life of Prince Sviatov is not the subject of any other medieval Moringian texts

(B) the author of Sviatovin intended it to provide as accurate a report about Prince Sviatov's exploits as

possible

(D) Sviatovin is the earliest Moringian text whose composition can be dated to within a few years

(E) Sviatovin was not written by Sviatov's father himself

Argument Construction

Situation A medieval Moringian text was written about Prince Sviatov. It is not known exactly

when the text was written, but the events described in it occurred in 1165 and a diagram

in the text indicates that Sviatov's father—who died in 1167—was alive at the time it was

composed.

Reasoning What completion of the blank would provide the best reason for believing the argument's

conclusion? The argument's conclusion is that the book Sviatovin was written between

1165 and 1167. The reasoning given is this: It could not have been written before 1165

because it includes events that took place in that year. It could not have been written after

1167 because Sviatov's father died in that year. A diagram in the book suggests he was

alive when the book was written. Was the diagram correct in that suggestion? The

argument depends on assuming that it was.

A The argument focuses on one text and its date of composition. The argument does not need to

make any assumptions about other texts.

B The argument does not assume this. Issues about the accurate reporting of Sviatov's exploits (or

about the author's intention to report them accurately) are irrelevant to the argument, which

hinges on the accuracy of the diagram that accompanies the text. The diagram does not report

Sviatov's exploits.

C Correct. The reasoning in the argument assumes that the diagram was correct in representing the

Prince's father as still living when the text was composed. If his father was not living when the

text was written, then the information that his father actually died in 1167 is no guarantee that the

text was composed by then.

D See the explanation for answer choice (A) above. The degree of precision with which scholars have

succeeded in dating other Moringian texts is entirely irrelevant.

E The conclusion concerns when Sviatovin was written and not by whom it was written. If, contrary

to answer choice (E), it were known that the author was Sviatov's father, this would actually

provide strong support for the argument's conclusion. Thus answer choice (E) does not provide a

good reason for the argument's conclusion.

The correct answer is C.

40. Crowding on Mooreville's subway frequently leads to delays, because it is difficult for passengers to exit from

the trains. Subway ridership is projected to increase by 20 percent over the next 10 years. The Mooreville

Transit Authority plans to increase the number of daily train trips by only 5 percent over the same period.

Officials predict that this increase is sufficient to ensure that the incidence of delays due to crowding does not

increase.

Which of the following, if true, provides the strongest grounds for the officials' prediction?

(A) By changing maintenance schedules, the Transit Authority can achieve the 5 percent increase in train trips

without purchasing any new subway cars.

(B) The Transit Authority also plans a 5 percent increase in the number of bus trips on routes that connect to

subways.

available.

(D) Most of the projected increase in ridership is expected to occur in off-peak hours when trains are now

sparsely used.

(E) The 5 percent increase in the number of train trips can be achieved without an equal increase in Transit

Authority operational costs.

Argument Construction

Situation Ridership on the Mooreville subway, which often experiences delays due to crowding, is

expected to increase 20 percent over the next 10 years. Despite plans to increase the

number of daily trains only 5 percent during those 10 years, officials predict that delays

due to crowding will not increase.

Reasoning What would provide the strongest grounds for the officials' prediction that delays due to crowding

will not increase? Delays due to crowding probably would increase if the extra 20 percent

total ridership occurred at typically busy times, even if the total 5 percent increase in the

number of daily trains were to occur at those typically busy times. The increases in daily

trains would clearly not be enough to absorb the extra ridership. If the increase in

ridership were to occur at other times of day, however, perhaps when the subway trains

were less crowded overall, the system would be able to absorb the extra passengers

without an increase in delays due to crowding.

A While this supports the idea that the Transit Authority can economically increase the number of

train trips, it provides no information about whether the trains will be crowded.

B Increasing the number of bus trips on routes that connect to subways would be likely to lead to

more people to ride the subways. This makes it less likely that the officials' prediction—that

delays due to overcrowding will not increase—will turn out to have been accurate.

C This suggests that subway ridership will remain high, and thus that delays caused by

overcrowding will continue.

D Correct. This statement properly identifies a situation in which the officials' prediction is likely

to turn out to have been accurate. The ridership will be increasing during times when more

passengers will not create delays, since they will merely fill empty seats on existing trains.

E While this supports the idea that the Transit Authority can economically increase the number of

train trips, it provides no information about whether the trains will be crowded.

The correct answer is D.

41. Installing scrubbers in smokestacks and switching to cleaner-burning fuel are the two methods available to

Northern Power for reducing harmful emissions from its plants. Scrubbers will reduce harmful emissions more

than cleaner-burning fuels will. Therefore, by installing scrubbers, Northern Power will be doing the most that

can be done to reduce harmful emissions from its plants.

Which of the following is an assumption on which the argument depends?

(A) Switching to cleaner-burning fuel will not be more expensive than installing scrubbers.

(B) Northern Power can choose from among various kinds of scrubbers, some of which are more effective

than others.

(D) Harmful emissions from Northern Power's plants cannot be reduced more by using both methods together

than by the installation of scrubbers alone.

(E) Aside from harmful emissions from the smokestacks of its plants, the activities of Northern Power do not

cause signiﬁcant air pollution.

Argument Construction

Situation A power plant can reduce emissions by installing scrubbers and also by switching to

cleaner-burning fuel; installing scrubbers reduces emissions more than switching fuels.

By installing scrubbers, the company is doing the most that it can do.

Reasoning What assumption does the argument depend on? The assumption will be a statement that has

to be true in order for the argument's premises to provide a solid reason for believing its

conclusion. Here, the conclusion that the company is doing the most that it can do is

based on believing that choosing one or the other of the two options will be more

effective than choosing both options together. This argument assumes, then, that

installing the scrubbers alone is just as effective as both installing scrubbers and

switching to cleaner-burning fuel.

A The relative costs of the two options indicate nothing about whether by installing scrubbers the

company will have done the most that it can to reduce harmful emissions.

B Even if the company installs the most efficient scrubbers, it may be that there is more that

Northern Power could do to reduce harmful emissions.

C Even if the company is fully committed to reducing harmful emissions, it could be that installing

scrubbers is the most it can do to reduce harmful emissions.

D Correct. If harmful emissions could be reduced even more by using both methods, then

installing scrubbers alone will not be the most that the company can do to reduce harmful

emissions.

E Even if this were not assumed and the company's other activities did cause significant air

pollution, it could still be that installing scrubbers is the most that the company can do to reduce

harmful emissions from its plants; perhaps any of its other activities that do cause significant air

pollution have nothing to do with its plants—for example, pollution coming from trucks the

company uses.