GMAT 逻辑讲义
主讲：费允杰
欢迎使用新东方在线电子教材
第一章做题步骤
一、先读问题
二、再读文章
三、再看选项
第二章五大题型
一、归纳题
公共元素直推法。
if A then B 表示A充分的推出B（A→B）；
only if A then B 表示只有A才有B（B→A）；
规则：和only if 最接近的元素一定是必要条件，是箭头所指方向。
by A in order to B 表示A 推出B（A→B）；
must by A in order to B 表示B 推出A（B→A）；
规则：和must 最接近的元素一定是必要条件，是箭头所指方向。If only A, then B表示只有A才有B( A→B)；
Not A, unless B表示没有A 除非有B（A→B）；
A, unless B表示非B推出A或者非A推出B（B→A, A→B）；
A require B表示B是A的必要条件（A→B）；
A is necessary to B表示A是B成立的必需（B→A）；
A depend/draw/base on B表示B是A成立的必需（A→B）。
例1.所有的人都去了。我是人。
公共信息：人
直接推结论：我去了。
例2.To be mentally healthy, people must have self-respect. People can maintain self-respect only by continually earning the respect of others they esteem. They can earn this respect only by treating these others morally.
Which of the following conclusions can be properly drawn from the statements above?
(A) People who are mentally healthy will be treated morally by others.
(B) People who are mentally healthy will have treated morally those they esteem.
(C) People who are mentally healthy must have self-respect in other to be treated morally by others.
(D) People can expect to be treated morally by others only if they esteem these others.
(E) People who have self-respect seldom treat morally those esteem.
例3. Most television viewers estimate how frequently a particular type of accident or crime occurs by how extensively it is discussed on television news shows. Television news shows report more on stories that include dramatic pictures such as fires and motor vehicle accidents than they do on more common stories that have little visual drama such as bookkeeping fraud.
If the statements above are true, it can be properly concluded that which of the following is also true?
(A) The time television news reporters spend researching news stories is directly related to the number of viewers who will be affected by events like those in the news stories.
(B) It is easier for crimes such as bookkeeping fraud to go unprosecuted than it is crimes such as arson.
(C) The number of fires and motor vehicle accidents greatly increases after each television news show that includes dramatic pictures of a fire or motor vehicle accident.
(D) Viewers of television news show tend to overestimate the number of fires and motor vehicle accidents that occur relative to the number of crimes of bookkeeping fraud.
(E) The usual selection of news stories for television news show is determined by the number of news reporters available for assignment.
例1. 马克思说：“这本书只从资产阶级的角度去考虑问题，是不正确的。”
问：从文中能推出马克思认为这本书应从什么角度考虑问题？
(A)奴隶主阶级
(B)地主阶级
(C)工人阶级
(D)无产阶级
(E) 资产阶级以外的阶级
例2：Experienced pilots often have more trouble than novice pilots in learning to fly the newly developed ultra light airplanes. Being accustomed to heavier aircraft, experienced pilots, when flying ultra light craft, seem not to respect the wind as much as they should.
The passage implies that the heavier aircraft mentioned above are
(A) harder to land than ultra light aircraft
(B) not as popular with pilots as ultra light aircraft
(C) not as safe as ultra light aircraft
(D) more fuel-efficient than ultra light aircraft
(E) easier to handle in wind than ultra light aircraft
二、演绎题
（1）前提结论结构类型的文章
第一种题型：假设题
例1
New Jersey has one of the lowest motor vehicle fatality rates in the country, and it is one of the few states that require extensive annual automobile safety inspections. Therefore, all states should adopt similar safety inspection procedures. The argument above is based on which of the following assumptions?
(A) Most states tend to impose few rules and regulations on the automobile drivers operating within
those states.
(B) Most states are skeptical that annual automobile safety inspections can reduce fatality rates.
(C) Annual automobile safety inspections contribute significantly to holding down New Jersey’s fatality rate.
(D) Drivers in New Jersey are more safety conscious than are drivers in other parts of the country.
(E) A smaller number of people die on the roads in New Jersey than in most other states.
例2
The federal government expects hospitals to perform 10,000 organ transplants next year. But it is doubtful that this many donor organs will be available, since the number of fatalities resulting from car and motorcycle accidents has been dropping steadily over the past decade. The argument above makes which of the following assumptions?
(A) A significant number of the organs used in transplants come from people who die in car and motorcycle accidents.
(B) The number of car and motorcycle accidents will increase significantly during the next year.
(C) No more than 10,000 people will be in need of organ transplants during the next year.
(D) In the past the federal government’s estimates of the number of organ transplants needed during a given year have been very unreliable.
(E) For any given fatality resulting from a car or motorcycle accident, there is a hospital in the vicinity in need of an organ for a transplant.
例3
因为别人的老婆都有别墅，所以我也应该有别墅。
假设：我应该是别人的老婆。
例4
“On the whole,”Ms. Dennis remarked, “engineering students are lazier now that they used to be. I know because fewer and fewer of my students regularly do the work they are assigned.”The conclusion drawn above depends on which of the following assumptions?
(A) Engineering students are working less because, in a booming market they are spending more and more time investigating different job opportunities.
(B) Whether or not students do the work they are assigned is a good indication of how lazy they are.
(C) Engineering students should work harder than students in less demanding fields.
(D) Ms. Dennis’ students are doing less work because Ms. Dennis is not as effective a teacher as she once was.
(E) Laziness is something most people do not outgrow.
例5
A test of the National Weather Service’s stormdetecting radar systems found that the 1957 system is ten times more reliable than the new computerized system. Therefore the technology used in the new radar system must be less sophisticated than the radar technology used in the 1957 system. The conclusion drawn above depends on which of the following questionable assumptions?
(A) The reliability of storm-detecting radar systems is determined by the frequency of breakdowns.
(B) The level of sophistication of the technology used in storm-detecting radar system can be determined from the reliability of the system.
(C) The reliability of storm-detecting radar systems is determined by their accuracy in predicting weather patterns.
(D) Computer hardware is now a key component of the new storm-detecting radar systems used by weather forecasting services.
(E) Most of the significant advances in stormdetecting technology were made in the 1950s.
第二种题型：加强题
例1
Because incumbent members of Congress are given a great deal of attention by the news media and because they enjoy such perquisites as free mail privileges and generous travel allowances, incumbents enjoy an overwhelming advantage over their challengers in elections for the United States Congress. Which of the following, if true, best supports the claim above?
(A) In the last congressional elections, incumbents met with a larger number of lobbyists than did challengers.
(B) In the last congressional elections, 98 percent of the incumbents in the House of Representatives who were seeking reelection won.
(C) Incumbent members of Congress are frequently critical of the amount of attention given to them by the news media.
(D) The support that political station action committees provide to challengers for congressional seats often compensates for the perquisites enjoyed by incumbent members of Congress.
(E) Of all incumbent senators surveyed before the last congressional elections, 78 percent said that their challengers did not pose a serious threat to their chances for reelection.
例2
Which of the following, if true, would most strength the conclusion above?
(A)Many businesses that provide health insurance for their employees also provide seminars on stress management.
(B)Many businesses report a significant decrease in absenteeism during periods when employees feel pressured by management.
(C)There is a marked decrease in the number if complaints presented at college infirmaries during vacation time.
(D)There is a marked increase in the number of illness treated at college infirmaries around the time of examinations.
(E)Most people report that being in a hospital or an infirmary is a stressful situation.
第三种题型：削弱题
英文标志词：weaken, cast doubt, argue against, damage, counter, challenge, refute, jeopardize, undermine, drawback, flaw, criticism, reasoning error, weakness.
1）断桥型。A≠B
例1. Scientists now believe that artificial-hip implants, previously thought to be safe, may actually increase the risk of cancer in recipients after about 45 years of use. Though these implants do improve the quality of recipient’s lives, the increased risk of cancer is an unacceptable price to pay for these improvements. Therefore, they should be banned.
Which of the following, if true, is the strongest counterargument to the argument above?
(A) Artificial-hip implant surgery can severe complications, such as infection, chronic fever, and bone degeneration, and these complications can themselves be crippling or even fatal.
(B) Almost all artificial-hip implant recipients receive their implants at an age when they are unlikely to live more than an additional 30 years.
(C) Although artificial-hip implants increase the risk of cancer after about 45 year of use, a few of the cancers they induce are not fatal.
(D) Since artificial-hip implants are not very common, banning them would cause little hardship.
(E) Although the benefits of artificial-hip implant surgery have remained substantially the same over the past decade, the price of the surgery has risen considerably.
例2. Metropolis regulation limiting to four days the period during which milk can be sold to consumers after pasteurization is unreasonable. Under optimal conditions, pasteurized milk kept at 40 degrees. Fahrenheit remains unspoiled for at least 14 days. If Metropolis current limitation were changed to eight days, milk prices would drop, but product quality would be unaffected. Which of the following, if true, would most seriously weaken the conclusion drawn above?
(A) Most consumers keep milk no more than three days after purchase.
(B) A recent survey showed that 20 percent of Metropolis consumers favored extending the current limitation on the sale of milk to 8 days.
(C) Metr opolis’ grocery-store owners would prefer small, frequent deliveries of milk to larger, infrequent deliveries.
(D) Milk kept longer than 14 days after pasteurization generally presents no medical dangers if consumed.
(E) In Metropolis, conditions for handling and storing milk after pasteurization are seldom close to optimum.
2）他因型
例4. The excessive number of safety regulations that the federal government has placed on industry poses more serious hardships for big businesses than for small ones. Since large companies do everything on a more massive scale, they must alter more complex operations and spend much more money to meet government requirements.
Which of the following, if true, would most weaken the argument above?
(A) Small companies are less likely than large companies to have the capital reserve for improvements.
(B) The operations of small companies frequently rely on the same technologies as the operations of large companies.
(C) Safety regulation codes are uniform, established without reference to size of company.
(D) Large companies typically have more of their profits invested in other business than do small companies.
(E) Large companies are in general more likely than small companies to diversity the markets and products.
第四种题型：评价题
英文标志词：evaluate, appraisal.
当加强来做。
例. According to a recent survey, marriage is fattening. Cited as evidence is the survey's finding that the average woman gains 23 pounds and the average man gains 18 pounds during 13 years of marriage.
The answer to which of the following questions would be most relevant in evaluating the reasoning presented in the survey?
(A) Why was the period of time studied in the survey 13 years, rather than 12 or 14?
(B) Did some of the men surveyed gain less than 18 pounds during the time they were married?
(C) How much weight is gained or lost in 13 years by single people of comparable age to those surveyed?
(D) Were the woman surveyed as active as the men surveyed, at the time survey was made?
(E) Will the reported gains be maintained over the lifetimes of the persons surveyed?
补充习题
104. The cost of producing radios in Country Q is ten percent less than the cost of producing radios in Country Y. Even after transportation fees and tariff charges are added, it is still cheaper for a company to import radios fromCountry Q to Country Y than to produce radios in Country Y. The statements above, if true, best support which of the following assertions?
A. labor costs in Country Q are ten percent below those in Country Y.
B. importing radios from Country Q to Country Y will eliminate ten percent of the manufacturing jobs in Country Y.
C. the tariff on a radio imported from Country Q to Country Y is less than ten percent of the cost of manufacturing the radio in Country Y.
D. the fee for transporting a radio from Country Q to Country Y is more than ten percent of the cost of manufacturing the radio in Country Q.
E. it takes ten percent less time to manufacture a radios in Country Q than it does in Country Y.
66. Neither a rising standard of living nor balanced trade, by itself, establishes a country’s ability to comp ete in the international marketplace. Both are required simultaneously since standards of living can rise because of growing trade deficits and trade can be balanced by means of a decline in a country’s standard of living.
If the facts stated in the passa ge above are true, a proper test of a country’s ability to be competitive is its ability to ______
(A) balance its trade while its standard of living rises
(B) balance its trade while its standard of living falls
(C) increase trade deficits while its standard of living rises
(D) decrease trade deficits while its standard of living falls
(E) keep its standard of living constant while trade deficits rise.
101. For a trade embargo against a particular country to succeed, a high degree of both international accord and ability to prevent goods from entering or leaving that country must be sustained. A total blockade of Patria's ports is necessary to an embargo, but such an action would be likely to cause international discord over the embargo.
The claims above, if true, most strongly support which of the following conclusions?
(A) The balance of opinion is likely to favor Patria in the event of a blockade.
(B) As long as international opinion is unanimously against Patria, a trade embargo is likely to succeed.
(C) A naval blockade of Patria's ports would ensure that no goods enter or leave Patria.
(D) Any trade embargo against Patria would be likely to fail at some time.
(E) For a blockade of Patria's ports to be successful, international opinion must be unanimous.
59. To prevent some conflicts of interest, Congress could prohibit high-level government officials from accepting positions as lobbyists for three years after such officials leave government service. One such official concluded, however, that such a prohibition would be unfortunate because it
would prevent high-level government officials from earning a livelihood for three years.
The official’s conclusion logically depends on which of the following assumptions?
A. Laws should not restrict the behavior of former government officials.
B. Lobbyists are typically people who have previously been high-level government officials.
C. Low-level government officials do not often become lobbyists when they leave government service.
D. High-level government officials who leave government service are capable of earning a livelihood only as lobbyists.
E. High-level government officials who leave government service are currently permitted to act as lobbyists for only three years.
63. Even though most universiti es retain the royalties from faculty members’ inventions, the faculty members retain the royalties from books and articles they write. Therefore, faculty members should retain the royalties from the educational computer software they develop.
The conclusion above would be more reasonably drawn if which of the following were inserted into the argument as an additional premise?
A. Royalties from inventions are higher than royalties from educational software programs.
B. Faculty members are more likely to produce educational software programs than inventions.
C. Inventions bring more prestige to universities that do books and articles.
D. In the experience of most universities, educational software programs are more marketable that are books and articles.
E. In terms of the criteria used to award royalties, educational software programs are more nearly comparable to books and articles than to inventions.
81. A recent report determined that although only three percent of drivers on Maryland highways equipped their vehicles with radar detectors, thirty-three percent of all vehicles ticketed for exceeding the speed limit were equipped with them. Clearly, drivers who equip their vehicles with radar detectors are more likely to exceed the speed limit regularly than are drivers who do not.
The conclusion drawn above depends on which of the following assumptions?
(A) Drivers who equip their vehicles with radar detectors are less likely to be ticketed for exceeding the speed limit than are drivers who do not.
(B) Drivers who are ticketed for exceeding the speed limit are more likely to exceed the speed limit regularly than are drivers who are not ticketed.
(C) The number of vehicles that were ticketed for exceeding the speed limit was greater than the number of vehicles that were equipped with radar detectors.
(D) Many of the vehicles that were ticketed for exceeding the speed limit were ticketed more than once in the time period covered by the report.
(E) Drivers on Maryland highways exceeded the speed limit more often than did drivers on other state highways not covered in the report.
110. “Fast cycle time” is a strategy of designing a manufacturing organization to eliminate bottlenecks and delays in production. Not only does it speed up production,
but it also assures quality. The reason is that the bottlenecks and delays cannot be eliminated unless all work is done right the first time.
The claim about quality made above rests on a questionable presupposition that _____ (A) any flaw in work on a product would cause a bottleneck or delay and so would be prevented from occurring on a “fast cycle” production line
(B) the strategy of “fast cycle time” would require fundamental rethinking of product design
(C) the primary goal of the organization is to produce a product of unexcelled quality, rather than to generate profits for stockholders
(D) “fast cycle time” could be achieved by shaving time off each of the component processes in production cycle
(E) “fast cycle time” is a concept in business strategy t hat has not yet been put into practice in a factory
26. Male bowerbirds construct elaborately decorated nests, or bowers. Basing their judgment on the fact that different local populations of bowerbirds of the same species build bowers that exhibit different building and decorative styles, researchers have concluded that the bowerbirds’ building styles are a culturally acquired, rather than a genetically transmitted, trait.
Which of the following, if true, would most strengthen the conclusion drawn by the researchers?
(A) There are more common characteristics than there are differences among the bower-building styles of the local bowerbird population that has been studied most extensively
(B) Young male bowerbirds are inept at bower-building and apparently spend years watching their elders before becoming accomplished in the local bower style.
(C) The bowers of one species of bowerbird lack the towers and ornamentation characteristic of the bowers of most other species of bowerbird.
(D) Bowerbirds are found only in New Guinea and Australia, where local populations of the birds apparently seldom have contact with one another.
(E) It is well known that the song dialects of some songbirds are learned rather than transmitted genetically.
103. The average life expectancy for the United States population as a whole is 73.9 years, but children born in Hawaii will live an average of 77 years, and those born in Louisiana, 71.7 years. If a newlywed couple from Louisiana were to begin their family in Hawaii, therefore, their children would be expected to live longer than would be the case if the family remained in Louisiana.
Which of the following statements, if true, would most significantly strengthen the conclusion drawn in the passage?
A. As population density increases in Hawaii, life expectancy figures for that state are likely to be revised downward.
B. Environmental factors tending to favor longevity are abundant in Hawaii and less numerous in Louisiana.
C. Twenty-five percent of all Louisianans who move to Hawaii live longer than 77 years.
D. Over the last decade, average life expectancy has risen at a higher rate for Louisianans than for Hawaiians.
E. Studies show that the average life expectancy for Hawaiians who move permanently to Louisiana is roughly equal to that of Hawaiians who remain in Hawaii.
112. In tests for pironoma, a serious disease, a false positive result indicates that people have pironoma when, in fact, they do not; a false negative result indicates that people do not have pironoma when, in fact, they do. To detect pironoma most accurately, physicians should use the laboratory test that has the lowest proportion of false positive results.
Which of the following, if true, gives the most support to the recommendation above?
(A) The accepted treatment for pironoma does not have damaging side effects.
(B) The laboratory test that has the lowest proportion of false positive results causes the same minor side effects as do the other laboratory tests used to detect pironoma. (C) In treating pironoma patients, it is essential to begin treatment as early as possible, since even a week of delay can result in loss of life.
(D) The proportion of inconclusive test results is equal for all laboratory tests used to detect pironoma.
(E) All laboratory tests to detect pironoma have the same proportion of false negative results.
补充习题：削弱题
18. Opponents of laws that require automobile drivers and passengers to wear seat belts argue that in a free society people have the right to take risks as long as the people do not harm other as a result of taking the risks.As a result, they conclude that it should be each person’s decision whether or not to wear a seat belt.
Which of the following, if true, most seriously weakens the conclusion drawn above?
A. Many new cars are built with seat belts that automatically fasten when someone sits in the front seat.
B. Automobile insurance rates for all automobile owners are higher because of the need to pay for the increased injuries or deaths of people not wearing seat belts.
C. Passengers in airplanes are required to wear seat belts during takeoffs and landings.
D. The rate of automobile fatalities in states that do not have mandatory seat belt laws is greater than the rate of fatalities in states that do have such laws.
E. In automobile accidents, a greater number of passengers who do not wear seat belts are injured than are passengers who do wear seat belts.
27. A drug that is highly effective in treating many types of infection can, at present,
be obtained only from the bark of the ibora, a tree that is quite rare in the wild. It takes the bark of 5,000 tree to make one kilogram of the drug. It follows, therefore, that continued production of the drug must inevitably lead to the ibora’s extinction. Which of the following, if true, most seriously weakens the argument above?
(A) The drug made from ibora bark is dispensed to doctors from a central authority.
(B) The drug made from ibora bark is expensive to produce.
(C) The leaves of the ibora are used in a number of medical products.
(D) The ibora can be propagated from cuttings and grown under cultivation.
(E) The ibora generally grows in largely inaccessible places.
58. Insurance Company X is considering issuing a new policy to cover services required by elderly people who suffer from diseases that afflict the elderly. Premiums for the policy must be low enough to attract customers. Therefore, Company X is concerned that the income from the policies would not be sufficient to pay for the claims that would be made.
Which of the following strategies would be most likely to minimize Company X’s losses on the policies?
A.Attracting middle-aged customers unlikely to submit claims for benefits for many
years.
B.Insuring only those indiveduals who did not suffer any serious diseases as
children.
C.Including a greater number of services in the policy than are included in other
policies of lower cost.
D.Insuring only those individuals who were rejected by other companies for similar
policies.
E.Insuring only those individuals who are wealthy enough to pay for the medical
services.
61. The fewer restrictions there are on the advertising of legal services, the more lawyers there are who advertise their services, and the lawyers who advertise a specific service usually charge less for that service than the lawyers who do not advertise. Therefore, if the state removes any of its current restrictions, such as the one against advertisements that do not specify fee arrangemntes, overall consumer legal costs will be lower than if the state retains its current restrictions.
Which of the following, if true, would most seriously weaken the argument concerning overall consumer legal costs?
A.The state has recently removed some other restrictions that had limited the
advertising of legal services.
B.The state is unlikely to remove all the restrictions that apply solely to the
advertising of legal services.
https://www.doczj.com/doc/815042104.html,wyers who do not advertise generally provide legal services of the same quality
as those provided by lawyers who do advertise.
D.Most lawyers who now specify fee arrangements in their advertisements would
continue to do so even if the specification were not required.
E.Most lawyer who advertise specific services do not lower their fees for those
services when they begin to advertise.
62. During the Second World War, about 375,000 civilians died in the United States and about 408,000 members of the United States armed forces died overseas. On the basis of those figures, it can be conclded that it was not much more dangerous to be overseas in the armed forces during the Second World War than it was to stay at home as a civilian.
Which of the following would reveal most clearly the absurdity of the conclusion drawn above?
A.Counting deaths among members of the armed forces who served in the United
States in addition to deaths among members of the armen forces serving overseas.
B.Expressing the difference between the numbers of deaths among civilians and
members of the armed forces as a percentage of the total number of deaths.
C.Separating deaths caused by accidents during service in the armed forces from
deaths caused by combat injuries.
https://www.doczj.com/doc/815042104.html,paring death rates per thousand members of each group rather than
comparing total numbers of deaths.
https://www.doczj.com/doc/815042104.html,paring deaths caused by accidents in the United States to deaths caused by
combat in the armed forces.
64. Red blood cells in which the malarial-fever parasite resides are eliminated from a person’s body after 120 days. Because the parasite cannot travel to a new generation of red blood cells, any fever that develops in a person more than 120 days after that person has moved to a malaria-free region is not due to the malarial parasite.
Which is the following, if true, most seriously weakens the conclusion above?
A. The fever caused by the malarial parasite may resemble the fever caused by flu viruses.
B. The anopheles mosquito, which is the principal insect carrier of the malarial parasite, has been eradicated in many parts of the world.
C. Many malarial symptoms other than the fever, which can be suppressed with anti-malarial medication, can reappear within 120 days after the medication is discontinued.
D. In some cases, the parasite that causes malarial fever travels to cells of the spleen, which are less frequently eliminated from a person’s body than are red blood cells.
E. In any region infested with malaria-carrying mosquitoes, there are individuals who appear to be immune to malaria.
78. In comparison to the standard typewriter keyboard, the EFCO keyboard, which
places the most-used keys nearest the typist’s strongest fingers, allows faster typing and results in less fatigue. Therefore, replacement of standard keyboards with the EFCO keyboard will result in an immediate reduction of typing costs.
Which of the following, if true, would most weaken the conclusion drawn above? A.People who use both standard and EFCO keyboards report greater difficulty in the
transition from the EFCO keyboard to the standard keyboard than in the transition from the standard keyboard to the EFCO keyboard.
B.EFCO keyboards are no more expensive to manufacture than are standard
keyboards and require less frequent repair than do standard keyboards.
C.The number of businesses and government agencies that use EFCO keyboards is
increasing each year.
D.The more training amd experience an employee has had with the standard
keyboard, the more costly it is to train that employee to use the EFCO keyboard.
E.Novice typists can learn to use the EFCO keyboard in about the same amount of
time that it takes them to learn to use the standard keyboard.
105. The average normal infant born in the United States weighs between 12 and14pounds at the age of three months. Therefore, if a three-month-old child weighs only 10 pounds, its weight gain has been below the United States average.
Which of the following indicates a flaw in the reasoning above?
A. Weight is only one measure of normal infant development.
B. Some three-month-old children weigh as much as17 pounds.
C. It is possible for a normal child to weigh 10 pounds at birth.
D. The phrase “below average” does not necessarily mean insufficient.
E. Average weight gain is not the same as average weight.
109. Correctly measuring the productivity of service workers is complex. Consider, for example, postal workers: they are often said to be more productive if more letters are delivered per postal worker. But is this really true? what if more letters are lost or delayed per worker at the same time that more are delivered?
The objection implied above to the productivity measure described is based on doubts about the truth of which of the following statements?
(A) Postal workers are representative of service workers in general.
(B) The delivery of letters is the primary activity of the postal service.
(C) Productivity should be ascribed to categories of workers, not to individuals.
(D) The quality of services rendered can appropriately be ignored in computing productivity.
(E) The number of letters delivered is relevant to measuring the productivity of postal workers.
113. The difficulty with the proposed high-speed train line is that a used plane can be
bought for one-third the price of the train line, and the plane, which is just as fast, can fly anywhere. The train would be a fixed linear sustem, and we live in a world that is spreading out in all directions and in which consumers choose the free-wheel systems (cars, buses, aircraft), which do not have fixed routes. Thus a sufficient market for the train will not exist.
Which of the following, if true, most severely weakens the argument presented above?
A.Cars, buses, and planes require the efforts of drivers and pilots to guide them,
whereas the train will be guided mechanically.
B.Cars and buses are not nearly as fast as the high-speed train will be.
C.Planes are not a free-wheel system because they can fly only between airports,
which are less convenient for consumers than the high-speed train’s stations would be.
D.The high-speed train line cannot use currently underutilized train stations in large
cities.
E.For long trips, most people prefer to fly rather than to take ground-level
transportation.
补充习题：评价题
108. Although custom prosthetic bone replacements produced through a new computer-aided design process will cost more than twice as much as ordinary replacements, custom replacements should still be cost-effective. Not only will surgery and recovery time be reduced, but custom replacements should last longer, thereby reducing the need for further hospital stays.
Which of the following must be studied in order to evaluate the argument presented above?
(A) The amount of time a patient spends in surgery versus the amount of time spent recovering from surgery
(B) The amount by which the cost of producing custom replacements has declined with the introduction of the new technique for producing them
(C)The degree to which the use of custom replacements is likely to reduce the need for repeat surgery when compared with the use of ordinary replacements
(D) The degree to which custom replacements produced with the new technique are more carefullymanufactured than are ordinary replacements
(E) The amount by which custom replacements produced with the new technique will drop in cost as the production procedures become standardized and applicable on a larger scale
（2）因果结构类型的文章
因果结构文章的特点：A是前提，B是结论，B对A解释
标志词：due to，attribute to，result of，blame on/for，responsible for，credit to，explanation，interpratation，hypothesis
例1. The population of peregrine falcons declined rapidly during the 1950's and 1960's and reached an all-time low in the early 1970's. The decline was attributed by scientists to the widespread use of the pesticide DDT in rural areas.
Which of the following, if true, gives the strongest support to the scientists claim?
(A) DDT was not generally in use in areas devoted to heavy industry.
(B) In the time since the use of DDT was banned in 1972, the population of peregrine falcons has been steadily increasing.
(C) Peregrine falcons, like other birds of prey, abandon eggs that fallen out of the nest, even if the eggs remain intact.
(D) Starling, house sparrows, and blue jays-birds the peregrine falcon prey on-were not adversely affected by DDT in their habitats.
(E) Other birds of prey, such as the osprey, the bald cage, and the brown pclican, are found in the same area as is the peregrine falcon.
例. The price of maple syrup has jumped from 22 dollars a gallon three years ago to 40 dollars a gallon today. It can be concluded that maple-syrup harvesters have been artificially inflating prices and that governmental price regulations are necessary to control rising prices.
Which of the following, if true, casts the most doubt on the conclusion drawn above?
(A) The government already requires maple-syrup harvesters to submit their facilities to licensing by the health department.
(B) Insect infestation and drought have stunted the growth of syrup-producing maple trees and caused less-abundant syrup harvests.
(C) Maple syrup is produced in rural areas that suffer from high unemployment.
(D) Technological improvements in maple-syrup harvesting have reduced production costs.
1）削弱：寻找他因来解释前提，这个他因与结论没有直接的关系；还可以使用异因同果或同因异果的方法，这相当于断桥型削弱，将原因取非或结果取非就是正确答案
2）加强：事实型加强是正确的；桥梁型加强；异因异果型加强
例2. The presence of microorganisms that produce a toxin cause sweater to turn brownish red, phenomenon known as a red ride. Sea otters do not feed in areas where clams, their main source of food, have become contaminated with this toxin. According to a proposed explanation of the otter's behavior, the otters sample the clams in a potential feeding area and can taste any toxin in them.
Which of the following, if true, would most strongly indicate that the hypothesis described in the last sentence of the passage of the passage is not correct?
(A) In some of the area where red tides occur, neither clams nor sea otters are indigenous species.
(B) The presence of sea otters in a given area has a significant effect on which other
marine organisms are to be found in that areas.
(C) When seawater in an area unaffected by red tide is artificially dyed brownish red, sea otters do not feed on the clams in that area.
(D) If the clams in a given areas are contaminated with toxin, sea otters move to other areas in search of food.
(E) Although very small amounts of the toxin produced during a red tide are not harmful, large doses can be fatal to animals the size of sea otters.
例3. Since 1945 there have been numerous international confrontations as tense as those that precipitated the Second World War, and yet no large-scale conflict has resulted. To explain this, some argue that fear of enormous destruction such as the Second War produced has had a dramatic deterrent effect.
Which of the following, if true, most seriously weakens the deterrent theory mentioned above?
(A) After the First World War, the fear of great future destruction was as intense as it was after the Second World War.
(B) Psychologists have determined that the fear of retaliation tends to temper aggressiveness among human beings.
(C) The Second World War was far less distractive than most people generally believe.
(D) Fear of repeating the levels of destruction that the Second World War produced is as pervasive today as it was forty years ago.
(E) Many of the international confrontations that have occurred since 1945 have involved countries that participated in the Second World War.
加强：
例1. The population of peregrine falcons declined rapidly during the 1950's and 1960's and reached an all-time low in the early 1970's. The decline was attributed by scientists to the widespread use of the pesticide DDT in rural areas.
Which of the following, if true, gives the strongest support to the scientists claim?
(A) DDT was not generally in use in areas devoted to heavy industry.
(B) In the time since the use of DDT was banned in 1972, the population of peregrine falcons has been steadily increasing.
(C) Peregrine falcons, like other birds of prey, abandon eggs that fallen out of the nest, even if the eggs remain intact.
(D) Starling, house sparrows, and blue jays-birds the peregrine falcon prey on-were not adversely affected by DDT in their habitats.
(E) Other birds of prey, such as the osprey, the bald cage, and the brown pclican, are found in the same area as is the peregrine falcon.
例2. The town of Stavanger, Norway, was quiet and peaceful until early 1960's, when Stavanger became Norway's center for offshore oil exploration. Between then and now, violent crime and vandalism in Stavanger have greatly increased. Clearly, these social problems are among the results of Stavanger's oil boom.
Which of the following, if it occurred between the early 1960's and now, gives the strongest support to the argument above?
(A) The people of Stavanger rarely regret that their town was chosen to be Norway's center for offshore oil exploration.
(B) Norwegian sociologists expressed grave concern about the increase in violent crime and vandalism in Stavanger.
(C) Violent crime and vandalism have remained low in Norwegian that had no oil boom.
(D) Nonviolent crime, drug addiction, and divorce in Stavanger increased approximately as much as violent crime and vandalism did.
(E) The oil boom necessitated the building of wider roads for the increased traffic in Stavanger.