[外语类试卷]大学英语六级模拟试卷833及答案与解析.doc
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1、大学英语六级模拟试卷 833及答案与解析 一、 Part I Writing (30 minutes) 1 For this part, you are allowed 30 minutes to write a short essay entitled The Importance of Information Security. You should write at least 150 words following the outline given below. 1很多人认为信息安全很 重要 2有的人认为信息不是实物,所以信息安全无关紧要 3我认为 The Importance of
2、 Information Security 二、 Part II Reading Comprehension (Skimming and Scanning) (15 minutes) Directions: In this part, you will have 15 minutes to go over the passage quickly and answer the questions attached to the passage. For questions 1-4, mark: Y (for YES) if the statement agrees with the inform
3、ation given in the passage; N (for NO) if the statement contradicts the information given in the passage; NG (for NOT GIVEN) if the information is not given in the passage. 1 Think or Swim: Can We Hold Back the Oceans? As the world gets warmer, sea levels are rising. It has been happening at a snail
4、s pace so far, but as it speeds up more and more low-lying coastal land will be lost. At risk are many of the worlds cities and huge areas of fertile farmland. The sea is set to rise a metre or more by the end of this century. And thats just the start. “Unless there is a rapid and dramatic about-fac
5、e in emissions which no one expects the next century will be far worse than this century,“ says glaciologist(冰川学家 )Bob Bindshadler of NASAs Goddard Space Flight Center, Maryland. Throwing trillions of dollars at the problem could probably save big cities such as New York and London, but the task of
6、defending all low-lying coastal areas and islands seems hopeless. Or is it? Could we find a way to slow the accelerating glaciers, drain seas into deserts or add more ice to the great ice caps of Greenland and Antarctica? These ideas might sound crazy but we have got ourselves into such a bad situat
7、ion that maybe we should start to consider them. If we carry on as we are, sea levels will rise for millennia, probably by well over 10 metres. Slashing greenhouse gas emissions would slow the rise, but the longer we hesitate, the bigger the rise we will be committed to. Even if “conventional“ geo-e
8、ngineering schemes for cooling the planet were put in place and worked as planned, they would have little effect on sea level over the next century unless combined with drastic emissions cuts. In short, if coastal dwellers dont want their children and grandchildren to have to abandon land to the sea
9、, now is the time to start coming up with Plan C. So New Scientist set out in search of the handful of researchers who have begun to think about specific ways to hold back the waters. One of the reasons why the great ice sheets of Greenland and Antartica are already shrinking is that the ice is drai
10、ning off the land faster. Ice floating on the surrounding seas usually acts as a brake, holding back glaciers on land, so as this ice is lost the glaciers flow faster. The acceleration of the Jakobshavn glacier in Greenland is thought to be the result of warm currents melting the floating tongue of
11、the glacier. Other outlet glaciers are being attacked in a similar way. Mike MacCracken of the Climate Institute in Washington DC is one of those starting to think that we shouldnt just sit back and let warm currents melt ice shelves. “Is there some way of doing something to stop that flow, or cool
12、the water?“ he asks. Last year, physicist Russel Seitz at Harvard University suggested that the planet could be cooled by using fleets of customised boats to generate large numbers of tiny bubbles. This would whiten the surface of the oceans and so reflect more sunlight. MacCracken says the bubbles
13、might be better arranged in a more focused way, to cool the currents that are undermining the Jakobshavn glacier and others like it. A couple of degrees of chill would take this water down to freezing point, rendering it harmless. “At least that would slow the pace of change,“ MacCracken says. What
14、about a more direct approach: building a physical barrier to halt a glaciers flow into the sea by brute force? Bindshadler thinks that is a non-starter. “The ice discharge has many sources, mostly remote and in environments where barriers are not likely to work,“ he says. “Taking just the one exampl
15、e I know best, the Pine Island glacier in Antarctica drains into an ice shelf that at its front is 25 kilometres across and 500 metres thick, and moves at over 10 metres per day. The seabed there is 1000 metres down and is made of sediment(沉淀物 )hundreds of metres thick and the consistency of toothpa
16、ste.“ Not your ideal building site. A slightly more subtle scheme to rein in the glaciers was proposed more than 20 years ago by Douglas MacAyeal of the University of Chicago. His idea is to fight ice with ice. The big outlet glaciers feed into giant floating shelves of ice, which break off into ice
17、bergs at their outer edges. MacAyeal suggested pumping water up from beneath the ice and depositing it on the upper surface, where it would freeze to form a thick ridge, weighing down the floating ice shelf. Add enough ice in this way, and the bottom of the ice shelf would eventually be forced down
18、onto the seabed. Friction with the seabed would slow down the shelf s movement, which in turn would hold back the glaciers feeding into it. It would be like tightening an immense valve. “I think its quite an inspired idea,“ says Bindshadler. But nobody has followed it up to work out how practical th
19、e scheme would be. “On the back of an envelope it has promise but these ice shelves are big. You would need a lot of drilling equipment all over the ice shelf, and my intuition is that if you look at the energetics of it, it wont work,“ Bindshadler says. Even if we could apply brakes to glaciers, th
20、is would only slow down sea level rise. Could we do better than that and reverse it actually make the sea retreat? If you think of the sea as a giant bathtub, then the most obvious way to lower its level is to take out the plug. “One of the oldest notions is filling depressions on the land,“ says Ma
21、cCracken. Among the largest of these is the Qattara depression in northern Egypt, which at its lowest point is more than 130 metres below sea level. Various schemes have been proposed to channel water from the Mediterranean into the depression to generate hydroelectric(水力的 )power, and as a by-produc
22、t a few thousand cubic kilometres of the sea would be drained away. Unfortunately, thats only enough to shave about 3 millimetres off sea level: a drop in the ocean. And there would be grave consequences for the local environment. “The leakage of salt water through fracture systems would add salt to
23、 aquifers(含水层 )for good,“ says Farouk El-Baz, a geologist at Boston University who has studied the region. Refilling the Dead Sea is no better. Because of surrounding hills, this depression could be filled to 60 metres above sea level, but even that would only offset the rise by 5 millimetres and dr
24、own several towns into the bargain. The notion of engineering lower sea levels remains a highly abstract topic. “If the world doesnt control emissions, Im pretty sure that no geo-engineering solution will work and it would potentially create other side effects and false promises,“ says MacCracken. “
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- 外语类 试卷 大学 英语六级 模拟 833 答案 解析 DOC
