备考：
The country of Maravia has severe air pollution, 80 percent of which is caused by the exhaust fumes of cars. In order to reduce the number of cars on the road, the government is raising taxes on the cost of buying and running a car by 20 percent. This tax increase, therefore will significantly reduce air pollution in Maravia.
Which of the following, if true, most seriously weakens the argument above?
解释：此题中is caused by和therefore表明其逻辑关系：因为城市中80%的污染是由过多的尾气排放导致的。政府正在提高买车和养车的费用20%，希望借此降低汽车的数量。所以，作者认为这样可以降低城市的污染。想削弱此命题有以下几种思路：
1、 该国的80%污染并非来自于汽车尾气;
2、 提高买车和养车费用并不会减少车的数量，于是不能降低污染;
任何一个选项应与上面的内容相关。
(A) The government of Maravia is in the process of building a significant number of roadways.
(B) Maravia is an oil-producing country and is able to refine an amount of gasoline sufficient for the needs of its pollution.
(C) Maravia has had an excellent public transportation system for many years.
(D) Ninety percent of the population of Maravia is very prosperous(富有) and has a substantial amount of disposable
income.(可支配收入)
(E) In Maravia, cars that emit relatively low levels of pollutions cost 10 percent less to operate, on average, than do cars that emit high levels of pollutions.
削弱了文章手段达到目的的可能性。
II.解题方法2： 它因法，即其它因素导致了结论而并非文中的那个原因
例子12：
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?
解释：此题中Since表明其逻辑关系：因为大公司的规模效应所带来的更复杂的操作和更多的开销。所以，作者认为关于安全的规定对大公司影响比小公司大。想削弱此命题有以下几种思路：
1、 否定前提：大公司的规模效应不会带来更多复杂的操作以及更多的开销。
2、 否定结论：小公司比大公司更容易受到安全规定的影响，即选一个对小公司不利的选项。
任何一个选项应与上面的内容相关。
(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. 但这并不等于对于大公司来说不会带来更多的开销
(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.
8.解释题
例子13：
The population of elephant seals, reduced by hunting to perhaps a few dozen animals early in this century, has soared under federal protection during the last few decades. However, because the species repopulated itself through extensive inbreeding, it now exhibits a genetic uniformity that is almost unparalleled in other species of mammals, and thus it is in far greater danger of becoming extinct than are most other species.
Given the information in the passage above, which of the following is most likely the reason that other species of mammals are less likely than elephant seals to become extinct?
解释：此题中because和thus表明其逻辑关系：因为象海豹近亲繁殖而导致的遗传单一性。所以，作者认为象海豹相对于其它种群更容易有灭绝的危险。题目问的是其它的哺乳类动物没有象海豹那样容易灭绝的原因。答案必须跟遗传有关。
解释题的解答依靠常识
(A) Other species of mammals have large populations, so the loss of a few members of the species is not significant.
(B) Other species of mammals have increased their knowledge of dangers though the experience of generation after generation of animals.
(C) In other species of mammals, hunters can readily distinguish between males and females or between young animals and adults.
(D) In other species of mammals, some members of the species are genetically better equipped to withstand a disease or event that destroys other members of the species.
(E) Other species of mammals have retained habits of caution and alertness because they have not been protected as endangered species.
I.解释矛盾：
例子14：
During the day in Lake Constance, the zooplankton D. hyalina departs for the depths where food is scarce and the water cold. D. galeata remains near the warm surface where food is abundant. Even though D. galeata grows and reproduces much faster, its population is often outnumbered by D. hyalina.
Which of the following, if true, would help resolve the apparent paradox presented above?
解释：此题中奇怪现象就是h白天沉入食物少，水温低的湖底，而g留在食物丰富
的湖面。但是h的数量多于g。
任何一个选项应该能够解释h的数量比g多，或者g的数量比h少。
A The number of species of zooplankton living at the bottom of the lake is twice that of species living at the surface.
B Predators of zooplankton, such as whitefish and perch, live and feed near the surface of the lake during the day.
C In order to make the most of scarce food resources, D. hyalina matures more slowly than D. galeata.
D D. galeata clusters under vegetation during the hottest part of the day to avoid the Sun’s rays.
E D. galeata produces twice as many offspring per individual in any given period of time as does D. hyalina. 该选项刚好相
反
例子15：
For the United Stats meat industry, there is good news and bad news. The bad news in that over the last three years people in the United States have been eating less meat. The good news is that during this same time period meat producer’s profits have risen steadily.
Which of the following, if true during the last three years, contributes most to a resolution of the apparent discrepancy above?
解释：，可是美国的肉类生产商的利润
却稳步上升。 解题思路如下，利润必然和需求和价格有关。
1、肉类价格上升所带来的正面影响超过了由于消耗量下降所带来的负面影响 2、美国的消耗量是少了，其它地方的需求量上升了。
(A) People have been eating less meat because they are more health conscious than in the past. (B) In the United States many new restaurants that specialize in vegetarian meals have opened.
以上两个选项解释了为什么美国人的肉类消耗量下降，但是没能解释为什么利润却上升了。
(C) Competition from the growing fish industry has forced meat producers to sell meat at bargain prices in an attempt to
attract more consumers. 与价格应该上升相反
(D) Countries that are unable to produce enough meat for their populations have become a new and lucrative market for
United States meat producers.正好讲到需求量上升
(E) Meat producers have invested large amount of money on advertising in order to win back consumers who have
decreased their meat consumption. ”在广告上化很多钱“ 倒是说明了为什么肉类行业的利润下降(而不是上升)，因为增加了一块新的支出。
9.填空题
例子16：
Observations of the Arctic reveal that the Arctic Ocean is covered by less ice each summer than the previous summer. If this warming trend continues, within 50 years the Arctic Ocean will be ice free during the summer months. This occurrence would in itself have little or no effect on global sea levels, since the melting of ice floating in water does not affect the water level. However, serious consequences to sea levels would eventually result, because __________.
Which of the following most logically completes the passage?
解释：此题说道水中融化的冰本身对于海平面没有什么影响。但是从文章最后一
句应该可以知道肯定是其它因素导致了海平面的变化。
A large masses of floating sea ice would continue to form in the wintertime 此种因素不会对海平面有太大的影响 B significant changes in Arctic sea temperatures would be accompanied by changes in sea temperatures in more temperate parts of the world
C such a warm Arctic Ocean would trigger the melting of massive land- based glaciers in the Arctic
D an ice-free Arctic Ocean would support a very different ecosystem than it does presently E in the spring, melting sea ice would cause more icebergs to be created and to drift south into shipping routes
因此此题选择C，其它没有讲到其它可能会引起海平面变化的因素。
10.句子作用题
例子17：
At a certain period in Earth’s history, its atmosphere contained almost no oxygen, although plants were producing vast quantities of oxygen. As a way of reconciling these two facts, scientists have hypothesized that nearly all of the oxygen being produced was taken up by iron on Earth’s surface. Clearly, however, this explanation is inadequate. New studies show that the amount of iron on Earth’s surface was not sufficient to absorb anywhere near as much oxygen as was being produced.Therefore, something in addition to the iron on Earth’s surface must have absorbed much of the oxygen produced by plant life.
In the argument given, the two portions in boldface play which of the following roles?
解释：文中说道科学家假设地球表明的铁吸收了植物产生的氧气。但“这个解释不
充分”。“新的研究表明地表的铁远远不足以吸收那些氧气”。明显是前果后因的关系。
A The first is a claim made by the argument in support of a certain position; the second is that position. (此选项谈到第一句话支持第二句话)
B The first is a judgment made by the argument about a certain explanation; the second is that explanation.
C The first expresses the argument’s dismissal of an objection to the position it seeks to establish; the second is that position.
D The first sums up the argument’s position with regard to a certain hypothesis; the second provides grounds for that
position.
E The first is a concession by the argument that its initial formulation of the position it seeks to establish requires modification; the second presents that position in a modified form.
因此，此题选择D。