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根据材料请回答 23～30
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 visi-ble 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 to maintain a constant average temperature, such emissions from the planet must balance in- coming solar radiation.If there were no carbon dioxide in the atmosphere, heat would es-cape 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 a- bout 15 percent in the 1st hundred years, and we continue to add carbon dioxide to the at- mosphere.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 of ——18℃ can be observed at an altitude of 5 to 6 kilometers above the Earth.Below this altitude (called the radiating level), the tem- perature increases by about 6~C per kilometer approaching the Earth' s surface, where the average temperature is about 15~C．An increase in the amount of carbon dioxide means that there are more molecules of carbon dioxide to absorb infrared radiation.As the capaci- ty of the atmosphere to absorb infrared radiation increase, the radiating level and the.tem- perature of the surface must rise.
One mathematical model predicts that doubling the atmospheric carbon dioxide would raise the global mean surface temperature by 2.5℃.This model assumes that the atmos- phere 's relative humidity remains constant and the temperature decreases with altitude at a rate of 6.5~C 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.There- fore, more infrared radiation would be absorbed and reradiated back to the Earth's sur- face.The resultant warming at the surface could be expected to melt snow and ice, reduc- ing the Earth's reflectivity.More solar radiation would then be absorbed, leading to a fur-ther increase in temperature.
第 23 题 Paragraph 1
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The designers of the VLT are surprised at____________
根据材料请回答 41～45
Live with Computer
After too long on the Net, even a phone call can be a shock.My boyfriend's Liver-pudlian(利物普人的)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 it-self 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 re-lationship is computer-mediated(以电脑为媒介的).
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(杂货).
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(节点)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.
第 41 题 Compared to the clear words of her boyfriend on screen, his accent becomes__________.
Though not stated, the author implies that
Cloning (克窿 ): Future Perfect？
1．A clone is an exact copy of a plant or animal produced from any one cell. Since Scottish scientists reported that they had managed to clone a sheep named Dolly in 1997,research .into cloning has grown rapidly. In May 1998, scientists in Massachusetts managed to create two identical calves (牛犊) using cloning technology. A mouse has also been cloned successfully. But the debate over cloning humans really started when Chicago physicist Richard Seed made a surprising announcement: "We will have managed to clone a human being within the next two years," he told the world.
2．Seed's announcement provoked a lot of media attention, most of it negative. In Europe, nineteen nations have already signed an agreement banning human cloning and in the US the President announced: "We will be introducing a law to ban all human cloning and many states in the US will have passed anti-cloning laws by the end of the year."
3．Many researchers are not so negative about cloning. They are worried that laws banning human cloning will threaten important research. In March, The New England Journal of Medicine called any plan to ban research on cloning humans seriously mistaken. Many researchers also believe that in spite of attempts to ban it, human cloning will have become routine by 2010 because it is impossible to stop the progress of science.
4．Is there reason to fear that cloning will lead to a nightmare world？ The public has been bombarded (轰炸) with newspaper articles, television shows and films, as well as cartoons. Such information is often misleading, and makes people wonder what on earth the scientists will be doing next.
5．Within the next five to ten years scientists will probably have found a way of cloning humans. It could be that pretty soon we will be able to choose the person that we want our child to look like. But how would-it feel to be a clone among hundreds, the anti-cloners ask. Pretty cool, answer the pro-cloners (赞成克窿的人).
第 23 题 Paragraph 1_____________
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