(2)表示因果关系的动词：result in(结果)，result from(由于，由……)，follow from(……结果)，base…on…(以……为基础)，be due to(由于);
(4)表示因果关系的副词：as a result，consequently等。
wher do pesticides(杀虫剂)fit into the picture of environmental disease? We have seen that they now pollute soil, water, and food, that they have the power to make our streams fishless and our gardens and woodlands silent and birdless. Man, however much he may like to pretend the contrary, is part of nature. Can he escape a pollution that is now so thoroughly distributed throughout our world? We know that even single exposures to these chemicals, if the amount is large enough, can cause extremely severe poisoning. But this is not the major problem. The sudden illness or death of farmers, farm workers, and others exposes to sufficient quantities of pesti-cides is very sad and should not occur. For the population as a whole, we must be more concerned with the delayed effects of absorbing small amounts of the pesticides that invisibly pollute our world.
Responsible public health officials have pointed out that the biological effects of chemicals are cumulative(积累的)over long periods of time, and that the danger to the individual may depend on the sum of the exposures received throughout his life-time. For these very reasons the danger is easily ignored. It is human nature to shake off what may seem to us a threat of future disaster. "Men are naturally mo.st impressed by diseases which have obvious signs,"says a wise physician, Dr. Rene Dubos, "yet some of their worst enemies slowly approach them unnoticed."
People tend to ignore the delayed effects of exposure to chemicals because____.
A. limited exposure to them does little harm to people's health
B. the present is more important for them than the future
C. the danger does not become apparent immediately
D. humans are capable of withstanding small amounts of poisoning
这道题考点涉及原因。如果阅读时圈划了有关因果关系提示词，这道题就比较容易做了。因果关系提示词在第二段第二句：For these very reasons the danger is easily ignored.由此可知本段的前部为答案所在：化学制品的生物作用是长期积累的结果;化学制品对人危害的大小取决于人一生中接收的剂量的多少。C项：“化学制品的危害没有立即显现出来”表达的正是这个意思，所以是正确答案。
It is likely that the dispute regarding flats versus(对，对抗)individual houses will continue to rage on for a long time as far as Britain is concerned. And it is unfortunate that there should be hot feelings on both sides whenever this subject is raised. Those who oppose the building of flats base their case primarily on the assumption(设想)that everyone prefers an individual home and garden and on the high cost per unit of accommodation. The latter ignores the higher cost of providing full services to a scat- tered community and the cost in both money and time of the journeys to work for the suburban resident.
Some people oppose the building of flats because
A. the living expenses for each individual family are higher
B. it involves higher cost compared with the building of houses
C. they believe people like to live in houses with gardens
D. the disposal of rubbish remains a problem for those living in flats
这道题考点同样涉及原因。根据题干中的关键词组0ppose the building of flats定位到含有原因表达法(base…on，意为“以……为根据”)的相关句：Those who oppose the building of flats base their case primarily on the assumption(设想)that everyone prefers an individual home and garden and on the high cost per unit of accommodation.反对建公寓的人最主要的根据是，人们都喜欢独居于带花园的住房中，由此可知C项为正确答案。
Even plants can run a fever, especially when they're under attack by insects or disease. But unlike humans, plants can have their temperature taken from 3,000 feet away -- straight up. A decade ago, adapting the infrared(红外线)scanning technolo-gy developed for military purposes and other satellites, physicist Stephen Paley came up with a quick way to take the temperature of crops to determine which ones are un-der stress. The goal was to let farmers precisely target pesticide(杀虫剂)spraying rather than rain poison on a whole field, which invariably includes plants that don't have pest(害虫)problems.
Even better, Paley's Remote Scanning Services Company could detect crop prob-lems before they became visible to the eye. Mounted on a plane flown at 3,000 feet at night, an infrared scanner measured the heat emitted by crops. The data were trans- formed into a color-coded map showing wher plants were running "fevers". Farmers could then spot-spray, using 50 to 70 percent less pesticide than they otherwise would.
The bad news is that Paley's company closed down in 1984, after only three years. Farmers resisted the new technology and long-term backers were hard to find.
But with the renewed concern about pesticides on produce, and refinements in infrared scanning, Paley hopes to get back into operation. Agriculture experts have no doubt the technology works. "This technique can be used on 75 percent of agricultural land in the United States, " says George Oerther of Texas A&M. Ray Jackson, who re- cently retired from the Department of Agriculture, thinks remote infrared crop scan- ning could be adopted by the end of the decade. But only if Paley finds the financial backing which he failed to obtain 10 years ago.
Infrared scanning technology may be brought back into operation because of
A. the desire of farmers to improve the quality of their produce
B. growing concern about the excessive use of pesticides on crops
C. the forceful promotion by the Department of Agriculture
D. full support from agriculture experts
根据题干中的关键词组"brought back into operation"找到原文相关句：But with the renewed concern about pesticides on produce, and refinements in infrared scan-ning, Paley hopes to get back into operation.但是随着人们重新关注杀虫剂对农产品的影响，以及红外线扫描技术的改进，Paley希望能重操旧业。由此可以推出B项为正确答案。这个考点与相关句中的原因状语(以with引导)相联系。
The application of infrared scanning technology to agriculture met with some diffi-culties due to
A. the lack of official support
B. its high cost
C. the lack of financial support
D. its failure to help increase production
话：第一句话提到将红外线扫描技术运用于农业遇到困难――Paley的公司于l984年关闭，第二句话叙述了其中的原因：Farmers: resisted the new technology and long-term backers were hard to find.农场主们抵制这项新技术，而且难以找到(投资方面的)长期支持者。由此可知C项为正确答案。
For every course that he follows a student is given a grade, which is recorded, and the record is available for the student to show to prospective employers. All this impo- ses a constant pressure and strain of work, but in spite of this some students still find time for great activity in student affairs. Elections to positions in student organizations arouse much enthusiasm. The effective work of maintaining discipline is usually per- formed by students who advise the academic authorities. Any student who is thought to have broken the rules, for example, by cheating has to appear before a student court. With the enormous numbers of students, the operation of the system does in- volve a certain amount of activity. A student who has held one of these positions of au- thority is much respected and it will be of benefit to him later in his career.
American university students are usually under pressure of work because
A. their academic performance will affect their future careers
B. they are heavily involved in student affairs
C. they have to observe university discipline
D.they want to run for positions of authority
本题问的是美国大学生通常承受压力的原因。相关句在前两句话――第二句指出：All this imposes a constant pressure and strain of work…这一切给学生造成持续的压力和紧张……，由此可知原因在前一句：For every course that he follows a student is given a grade, which is recorded, and the record is available for the student to show to prospective employers.学生上的每门课都有一个分数登记在册，而分数可以由学生拿给未来雇主看。A：“其学业表现会影响其未来的工作”与上句“分数可以由学生拿给未来雇主看(由其决定是否录用)”意思一致，为正确答案。第一句和第二句之间为因果关系(第一句为因，第二句为果)，但没有因果关系提示词，仍然成为考点，这种先因后果(无提示词)的结构值得考生注意。
Some students are enthusiastic for positions in student organizations probably because
A. they hate the constant pressure and strain of their study
B. they will then be able to stay longer in the university
C. such positions help them get better jobs
D. such positions are usually well paid
第三句谈到部分学生热衷于在学生组织中任职：Elections tO positions in student organizations arouse much enthusiasm.接着讨论了任职学生的作用，最后才提到了学生热衷于任职的原因：A student who has held one of these positions of authority is much respected and it will be of benefit tO him later in his career.任职的学生受人尊敬，并在未来工作中获益，由此可知C为正确答案。
The reason these two wonders of nature are so difficult for many adults to explain to children is that they are not very well understood by adults themselves. For exam-ple, did you know that the lightning we see flashing down to the earth from a cloud is actually flashing up to a cloud from the earth? Our eyes trick us into thinking we see a downward motion when it's actually the other way around. But then, if we believed only what we think we see, we'd still insist that the sun rises in the morning and sets at night.
We believe that lightning is a downward motion because
A. we were taught so by our parents from our childhood
B. we are deceived by our sense of vision
C. it is a common natural phenomenon
D. it is a truth proved by science
这仍然是测试隐性原因的一道考题，思路是在有关结果附近找有关原因。谈论"downward motion"的相关句为第三句：0ur eyes trick US into thinking we see a downward motion when it'S actually the other way around.由此可知人们认为闪电由上向下运动，是因为被视觉所骗，因此B项为正确答案。
After the violent earthquake that shook Los Angeles in 1994, earthquake scien-tists had good news to report: The damage and death toll(死亡人数)could have been much worse. More than 60 people died in this earthquake. By comparison, an earthquake of similar intensity that shook America in 1988 claimed 25,000 victims. Injuries and deaths were relatively less in Los Angeles because the quake occurred at 4:31 a.m. on a holiday; when traffic was light on the city's highways. In addition, changes made to the construction codes in Los Angeles during the last 20 years have strengthened the city's buildings and highways, making them more resistant to quakes. Despite the good news, civil engineers aren't resting on their successes. Pinned to their drawing boards are blue prints(蓝图)for improved quake-resistant buildings. The new designs should offer even greater security to cities wher earthquakes often take place. In the past, making structures quake-resistant meant firm yet flexible materials, such as steel and wood, that bend without breaking. Later, people tried to lift a build-ing off its foundation, and insert rubber and steel between the building and its founda-tion to reduce the impact of ground vibrations. The most recent designs give buildings brains as well as concrete and steel supports. Called smart buildings, the structures respond like living organisms to an earthquake's vibrations. When the ground shakes and the building tips forward, the computer would force the building to shift in the op- posite direction. The new smart structures could be very expensive to build. However, that wouldsave many lives and would be less likely to be damaged during earthquakes.
One reason why the loss of lives in the Los Angeles earthquake was comparatively low is that
A. new computers had been installed in the buildings
B. it occurred in the residential areas rather than on the highways
C. large numbers of Los Angeles residents had gone for a holiday
D. improvements had been made in the construction of buildings and highways