2.概括大意与完成句子：
The molecules of carbon dioxide in the Earth's atmosphere affect the heat balance of the Earth by acting as a one-way screen. Although these molecules allow radiation at visible wavelengths, where most of the energy of sunlight is concentrated, to pass through, they absorb some of the longer-wavelength infrared emissions radiated from the Earth's surface, radiation that would otherwise be transmitted back into space. For the Earth's surface, radiation that would otherwise be transmitted back into space. For the Earth to maintain a constant average temperature, such emissions from the planet must balance incoming solar radiation. If there were no carbon dioxide in the atmosphere, heat would escape from the Earth much more easily. The surface temperature would be so much lower that the oceans might be a solid mass of ice.
Today, however, the potential problem is too much carbon dioxide. The burning of fossil fuels and the clearing of the forests have increased atmospheric carbon dioxide by about 15 percent in the 1st hundred years, and we continue to add carbon dioxide to the atmosphere. Could the increase in carbon dioxide cause a global rise in average temperature and could such a rise have serious consequences for human society? Mathematical models that allow us to calculate the rise in temperature as a function of the increase indicate that the answer is probably yes.
Under present conditions a temperature can be observed at an altitude of 5 to 6 kilometers above the Earth. Below this altitude （called the radiating level）, the temperature increases by about per kilometer approaching the Earth's surface, where the average temperature is bout. An increase in the amount of carbon dioxide means that there are more molecules of carbon dioxide to absorb infrared radiation. As the capacity of the atmosphere to absorb infrared radiation increase, the radiating level and the temperature of the surface must rise.
One mathematical model predicts that doubling the atmospheric carbon dioxide would raise the global mean surface temperature. This model assumes that the atmosphere's relative humidity remains constant and the temperature decreases with altitude at a rate of per kilometer.
The assumption of constant relative humidity is important, because water vapor in the atmosphere is another efficient absorber of radiation at infrared wavelengths. Because warm air can hold more moisture than cool air, the relative humidity will be constant only if the amount of water vapor in the atmosphere increases as the temperature rises. Therefore, more infrared radiation would be adsorbed and reradiated back to the Earth's surface. The resultant warming at the surface could be expected to melt snow and ice, reducing the Earth's reflectivity. More solar radiation would then be absorbed, leading to a further increase in temperature.
23. Paragraph 1 ______
24. Paragraph 3 ______
25. Paragraph 4 ______
26. Paragraph 5 ______
A. The prediction of the model
B. The influence on temperature
C. The effect of carbon dioxide
D. The potential problem
E. The import of the assumption
F. The serious consequences
27. Nowadays, too much carbon dioxide ______.
28. The radiating level and the temperature of the surface must rise because of _____.
29. Only if the amount of water vapor in the atmosphere increases as the temperature rises, the atmosphere's relative humidity ______.
30. An increase in the amount of carbon dioxide means that there are more molecules of carbon dioxide ______.
A. will be constant
B. to absorb infrared radiation
C. is becoming the potential problem
D. prepare ourselves to be chemists, physicist
E. increasing capacity of the atmosphere to absorb infrared radiation
F. escape from the earth much more easily

3.阅读理解：
Sleep Loss and Its Effects
Mental fatigue can be as threatening as a heart attack. Recent evidence indicates that sleepiness is a leading cause of traffic and industrial accidents. “Human error causes between 60% and 90% of all workplace accidents, depending on the type of job,” observes biological psychologist David Dinges of the University of Pennsylvania. “And inadequate sleep is a major factor in human error” , other research suggests that sleep loss contributes to everything from drug abuse to poor grades in school.
A typical adult needs about eight hours of shut-eye a night to function effectively. By that standard, million of Americans are for a long time sleep deprived, trying to get by on six hours or even less. In many household cheating on sleep has become an unconscious and harmful habit. “In its mid form, it's watching Ted Koppel and going to bed late and then getting up early to get to the gym,” says Cornell's Pollak. In extreme cases people stay up most of the night, seeing how little sleep will keep them going. They try to compensate by sleeping late on weekends, but that makes up for only part of the shortfall. Over the months and years, some researchers believe, the imbalance builds up and the effects accumulate. “Most Americans no longer know what it feels like to the fully alert,” contends Dr. William Dement, director of Stanford University's Sleep Center. They go through the day in a sort of twilight zone; the eyes may be wade open, but the brain is partly shut down.
Single parent Dianna Bennett, 43, works as a nurse at a correctional facility in Gardner, Mass. To be able to spend time with her three children during the day, she works the night shift, a schedule that usually allows her no more than four hours of sleep, “My kids tell me I am always tired.” She says. Amy Schwartzman, 35, a law student at Yale University, gets up at 9 a.m. and then, she attends classes and simulated court and work as a research assistant, often does not get home until 10 p.m. Nights of throwing into bed at 3 a.m. makes her feel “as if my brain isn't moving as quickly as it should be.” Noting that the circles under her eyes keep getting darker, “My mother told me I look like a raccoon.” Says Schwartzman.
31. Sleep loss contributes to everything EXCEPT______.
A. drug abuse
B. poor school grades
C. work effect
D. accidents
32. According to the passage, on weekends some people always ______.
A. go to bed
B. go to bed early
C. get up late
D. get up early
33. Because of sleep loss, most American ______.
A. have wide open eyes
B. are not fully alert
C. try to sleep more
D. live in the twilight zone
34. Though not stated, the author implies that ______.
A. American drug abuse is connected with loss of sheep
B. American students' poor grades result from lack of sleep
C. Adequate sleep is necessary for people's health
D. Accidents in the states could be reduced by more sleep
35. In his passage, which of the following is NOT mentioned by the author?
A. How interesting American night life is.
B. How busy some Americans are.
C. Some Americans' attitude toward sleep.
D. People should have more sleep.

4.阅读理解：
Diseases of Agricultural Plants
Plants, like animals, are subject to diseases of various kinds. It has been estimated that some 30,000 different diseases attack our economic plant: forty are known to attack, and about as many attack wheat. The results of unchecked plant disease are all too obvious in countries which have marginal food supplies. The problem will soon be more widespread as the population of the world increases at its frightening rate. Even in countries which are now amply fed by their agricultural products, there could soon be critical food shortages. It is easy to imagine the consequences of some disastrous attack on one of the major crops; the resulting famines could kill millions of people, and the resulting hardship on other millions could cause political upheavals disastrous to the order of the world.
Some plants have relative immunity to a great many diseases, while others have a susceptibility to them. The tolerance of a particular plant changes as the growing conditions change. A blight may be but a local infection easily controlled, on the other hand it can attack particular plants in a whole region or nation. An example is the blight which killed virtually every chestnut tree in North American. Another is the famous potato blight in Ireland in the last century. As a result of that, it was estimated that one million people died of starvation and related ailments.
Plant pathologists have made remarkable strides in identifying the pathogens of the various diseases. Bacteria may invade a plant through an infestation of insect parasites carrying the pathogen. A plant can also be inoculated by man. Other diseases might be caused by fungus which attacks the plant in the form of a mold or smut or rust. Frequently such a primary infection will weaken the plant so that a secondary infection may result from its lack of tolerance. The symptoms shown may cause an error in diagnosis, so that treatment may be directed toward bacteria which could be the result of a susceptibility caused by a primary virus infection.
36. How many diseases are known to attack wheat?
A. Around 30,000.
B. Around 140.
C. Around 29,960.
D. Around 40.
37. According to this passage, which of the following would a plant disease result in if it was left unchecked?
A. A world war.
B. Border conflicts.
C. Rations of grain and meat.
D. Social upheavals.
38. What is the main idea of the second paragraph?
A. Some plants have relative immunity to a great many diseases, while others have a susceptibility to them.
B. The tolerance of a particular plant changes as the growing conditions change.
C. A blight killed virtually every chestnut tree in North American.
D. A blight may be a national infection.
39. According to the passage, some plant diseases can be prevented by ______.
A. killing parasites
B. inoculation
C. killing insects
D. improving growing conditions
40. Which of the following statements is not true?
A. Some plant diseases many be caused by bacteria.
B. Some plant diseases many be caused by pathogens.
C. Some plant diseases many be caused by fungus.
D. Symptoms are always helpful in identifying diseases.

5.阅读理解：
Live with Computer
After too long on the Net, even a phone call can be a shock. My boyfriend's Liverpudlian accent suddenly becomes indecipherable after the clarity of his words on screen; a secretary's tone seems more rejecting than I'd imagined it would be. Time itself becomes fluid — hours become minutes, and alternately seconds stretch into days. Weekends, once a highlight of my week, are now just two ordinary days.
For the last three years, since I stopped working as a producer, I have done much of my work as a telecommuter. I submit articles and edit them via E-mail and communicate with colleagues on Internet mailing lists. My boyfriend lives in U.K.; so much of our relationship is computer-mediated.
If I desired, I could stay inside for weeks without wanting anything. I can order food, and manage my money, love and work. In fact, at times I have spent as long as three weeks alone at home, going out only to get mail and buy newspapers and groceries.
But after a while, life itself begins to feel unreal. I start to feel as though I've merged with my machines, taking data in, spitting them back out, just another node on the Net. Others on line report the same symptoms. We start to strongly dislike the outside forms of socializing. We have become the Net opponents' worst nightmare.
What first seemed like a luxury, crawling from bed to computer, not worrying about hair, and clothes and face, has become an avoidance, a lack of discipline. And once you start replacing real human contact with cyber-interaction, coming back out of the cave can be quite difficult.
41. Compared to the clear words of her boyfriend on screen, his accent becomes ______.
A. unidentifiable
B. unbearable
C. unreal
D. misleading
42. The passage implies that the author and her boyfriend live in ______.
A. different cities in England
B. different countries
C. the same city
D. the same country
43. The author feels her life unreal because ______.
A. she has become a machine
B. she has to deal with data
C. she loses the interest in social life
D. she often has nightmares
44. What is the main idea of the last paragraph?
A. To live with computer is luxury.
B. To care about your appearance has become an avoidance
C. We should not be controlled by computers and the Internet.
D. Having computers, people do not need human contact anymore.
45. What is the author's attitude to the computer?.
A. She likes it because it is a very important means of communication.
B. She likes it because it is very convenient.
C. She dislikes it because TV is more attractive.
D. She dislikes it because it makes her life monotonous and boring.

6.补全短文：
The advantages and disadvantages of large population have long been subject of discussion among economists. __46__. To feed a large population, inferior land must be cultivated and the good land worked intensively. __47__. Other economists have argued that a large population gives more scope for specialization and the development of facilities such as ports, roads and railways, ___48__.
One of the difficulties in carrying out a worldwide birth control program lies in the fact that official attitudes to population growth vary from country to country depending on the level of industrial development and the availability of food and raw materials. In the developing country where a vastly expanded population is pressing hard upon the limits of food, space and natural resources, ___49___. In a highly industrialized society the problem may be more complex. A decreasing birth rate may lead to unemployment ____50__. When the pressure of population on housing declines, prices also decline and the building industry is weakened. Faced with considerations such as these, the government of a developed country may well prefer to see a slowly increasing population, rather than one which is stable or in decline.
A. which are not likely to be built unless there is a big demand to justify them
B. It has been argued that the supply of good land is limited
C. it will be the first concern of government to place a limit on the birth rate, whatever the consequences may be
D. Thus, each person produces less and this means a lower average income than could be obtained with a smaller population.
E. A small population may mean lower productivity, but a higher average income
F. because it results in a declining market for manufactured goods

7.完形填空：
Heart Attack
In the United States, and especially in big cities and rural areas, tens of thousands of people with hearts that should be good 51 to keep them alive die each year for lack of adequate first aid. In New York City, for example, a new study has shown that only one person in 100 outside of hospitals 52 after the heart suddenly stops pumping. In contrast, in Seattle, the survival 53 after such heart attacks is one in five.
“The difference can be traced 54 the effectiveness of the chain of survival,” Dr. Joseph P. Ornato said. “Each link in the 55 must be strong enough for many lives to be 56.”
The chain begins with an immediate telephone 57 for emergency help and the start within four minutes of the process needed for restarting the 58 working, by a family member or bystander. It continues with the prompt arrival within eight 59 ten minutes of a rescuer equipped with a special instrument that can shock the heart back to a normal rhythm. And it ends with the administration of advanced emergency care by nurses to maintain the heart's ability to survive until the doctor at the hospitals take 60.when one or more links in this chain fail or function too slowly, the 61 of a victim surviving heart attack falls rapidly. Because of widespread weaknesses in the chain of 62, experts in emergency heart care estimate that 20,000 to 80,000 people 63 needlessly of heart attack each year, a number comparable to the 55,000 killed annually in automobile 64.
One expert says, “Sending an emergency vehicle to a heart attack victim 65 the special equipment is like having policemen with guns but no bullets. They may put on a good show, but they lack the weapon needed to get the job done.”
51 A. much B. enough C. many D. too
52 A. dies B. stops C. survives D. wakes
53 A. speed B. thing C. people D. rate
54 A. to B. at C. form D. on
55 A. list B. process C. step D. chain
56 A. saved B. taken C. born D. accepted
57 A. number B. call C. line D. worker
58 A. person B. brain C. heart D. body
59 A. by B. to C. and D. toward
60 A. over B. about C. on D. out
61 A. cause B. start C. event D. chance
62 A. survival B. luck C. help D. death
63 A. live B. die C. survive D. come
64 A. production B. incidents C. accidents D. troubles
65 A. without B. at C. with D. by