一. 假设的因果关系实际不成立

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, if true, would most seriously weaken the conclusion drawn in the passage?

A. Insurance company statisticians do not believe that moving to Hawaii will significantly lengthen the average Louisianan’s life.

B. The governor of Louisiana has falsely alleged that statistics for his state are inaccurate.

C. The longevity ascribed to Hawaii’s current population is attributable mostly to genetically determined factors.

D. Thirty percent of all Louisianans can expect to live longer than 77 years.

E. Most of the Hawaiian Islands have levels of air pollution well below the national average for the United States


美国人口整体平均预期寿命为 73.9 岁，但夏威夷出生的儿童平均预期寿命为 77 岁，路易斯安那州出生的儿童则为 71.7 岁。因此，若一对来自路易斯安那州的新婚夫妇在夏威夷组建家庭，他们的孩子预期寿命将比留在路易斯安那州更长。

以下哪项如果为真，最能严重削弱上述结论？

A. 保险公司统计人员认为，移居夏威夷不会显著延长路易斯安那州人的平均寿命。

B. 路易斯安那州州长谎称该州的统计数据不准确。

C. 夏威夷现有居民的长寿主要归因于基因决定的因素。

D. 30% 的路易斯安那州人预期寿命会超过 77 岁。

E. 夏威夷群岛大部分地区的空气污染水平远低于美国全国平均水平。

结论：在夏威夷组建家庭的路易斯安那州夫妇，其孩子预期寿命会比留在本州更长。

削弱逻辑：孩子未必会更长寿，因为……

推理过程：人们默认长寿是夏威夷的居住环境导致的，但这一假设不成立。选项 C 指出，夏威夷居民的长寿实则源于基因因素，而非居住地点，因此移居夏威夷无法让外来夫妇的孩子获得更长寿命，直接削弱结论。


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.


反对要求汽车司机和乘客系安全带的人认为，在自由社会中，只要不伤害他人，人们有权选择冒险。因此他们得出结论：是否系安全带应取决于个人决定。

以下哪项如果为真，最能严重削弱上述结论？

A. 许多新车配备前排座位自动系安全带的功能。

B. 由于需支付未系安全带者增加的伤亡赔偿，所有车主的汽车保险费率都被提高了。

C. 飞机乘客在起飞和降落时被要求系安全带。

D. 无强制安全带法的州，汽车死亡率高于有此类法律的州。

E. 汽车事故中，未系安全带的乘客受伤人数多于系安全带的乘客。


推理过程：反对者假设不系安全带的行为不会影响他人，但选项 B 指出，未系安全带者的伤亡会导致保险公司提高所有车主的保费，间接伤害了其他合规车主的利益，打破了 “不伤害他人” 的假设，从而削弱结论。


二. 忽略导致结果的其他可能因素

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


疟原虫寄生的红细胞会在 120 天后从人体中清除。由于疟原虫无法转移到新一代红细胞中，因此一个人移居到无疟疾地区 120 天后出现的任何发热症状，都不可能是疟原虫引起的。

以下哪项如果为真，最能严重削弱上述结论？

A. 疟原虫引起的发热可能与流感病毒引起的发热症状相似。

B. 传播疟原虫的主要媒介 —— 按蚊，已在世界许多地区被根除。

C. 许多除发热外的疟疾症状（可通过抗疟药物抑制），在停药后 120 天内可能复发。

D. 在某些情况下，引起疟疾发热的疟原虫会转移到脾脏细胞中，而脾脏细胞被人体清除的频率低于红细胞。

E. 在任何有疟蚊滋生的地区，都存在对疟疾具有免疫力的人。


推理过程：论证仅基于 “疟原虫仅存在于红细胞中” 这一单一因素得出结论，但忽略了疟原虫可能寄生在其他细胞中的情况。选项 D 指出，疟原虫可转移到清除频率更低的脾脏细胞中，能在人体内存活超过 120 天，因此 120 天后的发热仍可能由疟原虫引起，削弱结论。


三. 比较对象本质不具有可比性

The imposition of quotas limiting imported steel will not help the big American steel mills. In fact, the quotas will help “mini-mills” flourish in the United States. Those small domestic mills will take more business from the big Americal steel mills than would have been taken by the foreign steel mills in the absence of quotas.

Which of the following, if true, would cast the most serious doubt on the claim made in the last sentence above?

(A) Quality rather than price is a major factor in determining the type of steel to be used for a particular application.

(B) Foreign steel mills have long produced grades of steel comparable in quality to the steel produced by the big American mills.

(C) American quotas on imported goods have often induced other countries to impose similar quotas on American goods.

(D) Domestic “mini-mills” consistently produce better grades of steel than do the big American mills.

(E) Domestic “mini-mills” produce low-volume, specialized types of steels that are not produced by the big American steel mills.


实施钢铁进口配额限制不会帮助美国大型钢铁厂。事实上，配额将有助于美国 “小型钢厂” 蓬勃发展。与无配额时外国钢厂相比，这些美国小型钢厂将从大型钢厂那里抢占更多业务。

以下哪项如果为真，最能严重质疑上述最后一句的主张？

A. 决定特定用途钢材类型的主要因素是质量而非价格。

B. 外国钢厂长期以来生产的钢材质量与美国大型钢厂相当。

C. 美国对进口商品的配额往往会引发其他国家对美国商品实施类似配额。

D. 美国小型钢厂生产的钢材质量始终优于大型钢厂。

E. 美国小型钢厂生产的是小批量、专用型钢材，而这些钢材并非美国大型钢厂所生产。


结论：小型钢厂将比无配额时的外国钢厂从大型钢厂抢占更多业务。

削弱逻辑：小型钢厂不会从大型钢厂抢占更多业务，因为……推理过程：论证默认小型钢厂与大型钢厂的产品具有可比性（可替代），但选项 E 指出，两者生产的钢材类型不同（小型钢厂生产专用钢材，大型钢厂不生产），因此小型钢厂抢占的并非大型钢厂的业务，二者不具有竞争可比性，削弱结论。


In the United States in 1986, the average rate of violent crime in states with strict gun-control laws was 645 crimes per 100,000 persons—about 50 percent higher than the average rate in the eleven states where strict gun-control laws have never been passed. Thus one way to reduce violent crime is to repeal strict gun control laws.

Which of the following, if true, would most weaken the argument above?

(A) The annual rate of violent crime in states with strict gun-control laws has decreased since the passage of those laws.

(B) In states with strict gun-control laws, few individuals are prosecuted for violating such laws.

(C) In states without strict gun-control laws, many individuals have had no formal training in the use of firearms.

(D) The annual rate of nonviolent crime is lower in states with strict gun-control laws than in states without such laws.

(E) Less than half of the individuals who reside in states without strict gun-control laws own a gun.


1986 年美国，实施严格枪支管制法的州，暴力犯罪平均率为每 10 万人 645 起，比从未实施严格枪支管制法的 11 个州的平均率高出约 50%。因此，减少暴力犯罪的一种方法是废除严格的枪支管制法。

以下哪项如果为真，最能削弱上述论证？

A. 实施严格枪支管制法的州，暴力犯罪年发生率自法律通过以来已有所下降。

B. 在实施严格枪支管制法的州，很少有人因违反此类法律而被起诉。

C. 在无严格枪支管制法的州，许多人未接受过正式的枪支使用培训。

D. 实施严格枪支管制法的州，非暴力犯罪率低于无此类法律的州。

E. 无严格枪支管制法的州，不到一半的居民拥有枪支。


推理过程：论证直接比较两类州的暴力犯罪率，但忽略了两者初始犯罪水平的差异。选项 A 指出，实施枪支管制法的州，犯罪率在法律通过后已下降 —— 这说明此类州原本的暴力犯罪率可能更高，现有数据无法证明 “废除管制法能减少犯罪”，两类州不具有公平可比性，削弱结论。


四. 混淆短期影响与长期影响

Treatment for hypertension forestalls certain medical expenses by preventing strokes and heart disease. Yet any money so saved amounts to only one-fourth of the expenditures required to treat the hypertensive population. Therefore, there is no economic justification for preventive treatment for hypertension.

Which of the following, if true, is most damaging to the conclusion above?

(A) The many fatal strokes and heart attacks resulting from untreated hypertension cause insignificant medical expenditures but not treating the disease at the right time leads to large economic losses,

(B) The cost, per patient, of preventive treatment for hypertension would remain constant even if such treatment were instituted on a large scale.

(C) In matters of health care, economic considerations should ideally not be dominant.

(D) Effective prevention presupposes early diagnosis, and programs to ensure early diagnosis are costly.

(E) The net savings in medical resources achieved by some preventive health measures are smaller than the net losses attributable to certain other measures of this kind.


高血压治疗通过预防中风和心脏病，可以避免部分医疗支出。然而，由此节省的费用仅相当于治疗高血压患者所需支出的四分之一。因此，高血压预防性治疗不存在经济合理性。

以下哪项如果为真，最能损害上述结论？

A. 未经治疗的高血压导致的许多致命中风和心脏病，虽医疗支出不高，但未及时治疗会造成巨大经济损失。

B. 即使大规模开展高血压预防性治疗，每位患者的治疗成本仍将保持不变。

C. 在医疗保健领域，经济因素理想情况下不应占主导地位。

D. 有效预防需以早期诊断为前提，而确保早期诊断的项目成本高昂。

E. 某些预防性健康措施节省的医疗资源净收益，小于其他措施造成的净损失。


推理过程：论证仅关注 “治疗成本与短期医疗支出节省” 的对比，忽略了长期经济影响。选项 A 指出，未经治疗的高血压会引发长期巨大经济损失（远超短期医疗支出），而预防性治疗可避免这些损失，从长期经济角度看具有合理性，削弱结论。


五. 混淆百分比与绝对数值

In the United States, of the people who moved from one state to another when they retired, the percentage who retired to Florida has decreased by three percentage points over the past ten years. Since many local businesses in Florida cater to retirees, these declines are likely to have a noticeably negative economic effect on these businesses and therefore on the economy of Florida.

Which of the following, if true, most seriously weakens the argument given?

(A) People who moved from one state to another when they retired moved a greater distance, on average, last year than such people did ten years ago.

(B) People were more likely to retire to North Carolina from another state last year than people were ten years ago.

(C) The number of people who moved from one state to another when they retired has increased significantly over the past ten years.

(D) The number of people who left Florida when they retired to live in another state was greater last year than it was ten years ago.

(E) Florida attracts more people who move from one state to another when they retire than does any other state.


在美国，退休后跨州迁移的人群中，退休后移居佛罗里达州的比例在过去十年下降了 3 个百分点。由于佛罗里达州许多本地企业以退休人员为服务对象，这种下降可能会对这些企业乃至佛罗里达州的经济产生明显的负面影响。

以下哪项如果为真，最能严重削弱上述论证？

A. 去年退休后跨州迁移的人群，平均迁移距离比十年前更远。

B. 去年从其他州退休移居北卡罗来纳州的人数比十年前更多。

C. 过去十年，退休后跨州迁移的总人数大幅增加。

D. 去年退休后离开佛罗里达州移居其他州的人数比十年前更多。

E. 佛罗里达州吸引的退休跨州迁移人口数量，超过美国任何其他州。


推理过程：论证将 “移居比例下降 3%” 等同于 “移居人数减少”，混淆了百分比与绝对数值。选项 C 指出，跨州迁移的总人数大幅增加 —— 即使移居佛罗里达州的比例下降 3%，其绝对人数仍可能比十年前更多，企业的服务对象未必减少，从而削弱经济受负面影响的结论。