1、大学英语六级改革适用（阅读）模拟试卷 256及答案与解析 Section C 0 The direct rays of the sun touch the equator and strike northward toward title Tropic of Cancer. In the Southern hemisphere winter has begun, and it is summer north of the equator. The sea and air grow warmer, the polar air of winter begins its gradual retrea
2、t. The northward shift of the sun also brings the season of tropical cyclones to the northern hemisphere, a season that is ending for the Pacific and India Oceans south of the equator. Along our coasts and those of Asia, it is time to look seaward, to guard against the seasons storms. Over the Pacif
3、ic, the tropical cyclone season is never quite over, but varies in intensity. Every year, conditions east of the Philippines send a score of violent storms howling toward Asia, but it is worst from June through October. Southwest of Mexico, a few Pacific hurricanes will grow during spring and summer
4、, but most will die at sea or perish over the desert or the lower California coast as squalls. Along our Atlantic and Gulf coasts, the hurricane season is from June to November. In an average year, there are fewer than ten tropical cyclones and six of them will develop into hurricanes. These will ki
5、ll 50 to 100 persons between Texas and Maine and cause property damage of more than $100 million. If the year is worse than average, we will suffer several hundred deaths, and property damage will run to billions of dollars. Tornadoes, floods, and severe storms are in season elsewhere on the contine
6、nt. Now, to these destructive forces must be added the hazard of the hurricane. From the National Hurricane Center in Miami, a radar fence reaches westward to Texas and northward to New England. It provides a 200-mile look into offshore disturbances. In Maryland, the giant computers of the National
7、Meteorological Center digest the myriad bits of data-atmospheric pressure, temperature, humidity, surface winds, and winds aloft-received from weather stations and ships monitoring the atmospheric setting each hour, every day. Cloud photographs from spacecraft orbiting the earth are received in Mary
8、land and are studied for the telltale spiral on the warming sea. The crew of United States aircraft over the Gulf of Mexico, Caribbean, and Atlantic watch the sky and wait for the storm that will bear a persons name. The machinery of early warning vibrates with new urgency as the season of great sto
9、rms begins. 1 The cyclone season of the Southern hemisphere _. （ A） is brought by the polar air of winter （ B） ends when winter comes to the Southern hemisphere （ C） virtually lasts throughout the year （ D） begins when the sun rays strike the Tropic of Cancer 2 What is true about the storms howling
10、towards Asia? （ A） They originate over the Pacific. （ B） They influence Southeast Asia most violently. （ C） They mainly grow during spring and summer. （ D） They usually perish off coast. 3 When the Pacific hurricanes reach the lower California, most of them will _. （ A） reduce their intensity （ B） i
11、ncrease their intensity （ C） cause much property damage （ D） result in great rain and floods 4 What can we learn about the National Hurricane Center in Miami? （ A） It mainly provides protection against hurricanes to Texas and New England. （ B） It warns the whole country against tornadoes, severe sto
12、rms and hurricanes. （ C） It consists of radars along the coast of the west and the north of U.S. （ D） It supervises the coastal areas stretching from Texas to New England. 5 The passage discusses most clearly about_. （ A） the factors that cause hurricanes （ B） the most risky areas that suffer hurric
13、anes （ C） the early warning system against hurricanes （ D） the remedies for property damage by hurricanes 5 In the atmosphere, carbon dioxide acts rather like a one-way mirror the glass in the roof of a greenhouse which allows the suns rays to enter but prevents the heat from escaping. According to
14、a weather experts prediction, the atmosphere will be 3 warmer in the year 2050 than it is today, if man continues to burn fuels at the present rate. If this warming up took place, the ice caps in the poles would begin to melt, thus raising sea level several meters and severely flooding coastal citie
15、s. Also, the increase in atmospheric temperature would lead to great changes in the climate of the northern hemisphere, possibly resulting in an alteration of the earths chief food-growing zones. In the past, concern about a man-made warming of the earth has concentrated on the Arctic because the An
16、tarctic is much colder and has a much thicker ice sheet But the weather experts are now paying more attention to West Antarctic, which may be affected by only a few degrees of warming: in other words, by a warming on the scale that will possibly take place in the next fifty years from the burning of
17、 fuels. Satellite pictures show that large areas of Antarctic ice are already disappearing. The evidence available suggests that a warming has taken place. This fits the theory that carbon dioxide warms the earth. However, most of the fuel is burnt in the northern hemisphere, where temperatures seem
18、 to be falling. Scientists conclude, therefore, that up to now natural influences on the weather have exceeded those caused by man. The question is: Which natural cause has most effect on the weather? One possibility is the variable behavior of the sun. Astronomers at one research station have studi
19、ed the hot spots and “cold“ spots (that is, the relatively less hot spots) on the sun. As the sun rotates, every 27.5 days, it presents hotter or “colder“ faces to the earth, and different aspects to different parts of the earth. This seems to have a considerable effect on the distribution of the ea
20、rths atmospheric pressure, and consequently on wind circulation. The sun is also variable over a long term: its heat output goes up and down in cycles, the latest trend being downward. Scientists are now finding mutual relations between models of solar-weather interactions and the actual climate ove
21、r many thousands of years, including the last Ice Age. The problem is that the models are predicting that the world should be entering a new Ice Age and it is not. One way of solving this theoretical difficulty is to assume a delay of thousands of years while the solar effects overcome the inertia (
22、惯性 ) of the earths climate. If this is right, the warming effect of carbon dioxide might thus be serving as a useful counter-balance to the suns diminishing heat. 6 It can be concluded that a concentration of carbon dioxide in the atmosphere would _. （ A） prevent the suns rays from reaching the eart
23、hs surface （ B） mean a warming up in the Arctic （ C） cause great climate changes in the northern hemisphere （ D） raise the temperature of the earths surface 7 The article was written to explain_. （ A） the greenhouse effect （ B） the solar effects on the earth （ C） the models of solar-weather interact
24、ions （ D） the causes affecting weather 8 Why is the fuel consumption greater in the northern hemisphere, but temperatures there seem to be falling? （ A） Mainly because the levels of carbon dioxide are rising. （ B） Possibly because the ice caps in the poles are melting. （ C） Because the inertia of th
25、e earths climate take effect. （ D） Partly because in the output of solar energy varies. 9 On the basis of their models, scientists are of the opinion that _. （ A） the climate of the world should be becoming cooler （ B） it will take thousands of years for the inertia of the earths climate to take eff
26、ect （ C） the man-made warming effect helps to increase the solar effects （ D） the new Ice Age will be delayed by the greenhouse effect 10 If the assumption about the delay of a new Ice Age is correct, _. （ A） the best way to overcome the cooling effect would be to burn more fuels （ B） ice would soon
27、 cover the northern hemisphere （ C） the increased levels of carbon dioxide could warm up the earth quickly （ D） the greenhouse effect could work to the advantage of the earth 10 “The worlds environment is surprisingly healthy. Discuss.“ If that were an examination topic, most students would tear it
28、apart, offering a long list of complaints: from local smog (烟雾 ) to global climate change, from the felling (砍伐 ) of forests to the extinction of species. The list would largely be accurate, the concern legitimate. Yet the students who should be given the highest marks would actually be those who ag
29、reed with the statement. The surprise is how good things are, not how bad. After all, the worlds population has more than tripled during this century, and world output has risen hugely, so you would expect the earth itself to have been affected. Indeed, if people lived, consumed and produced things
30、in the same way as they did in 1900 (or 1950, or indeed 1980), the world by now would be a pretty disgusting place: smelly, dirty, toxic and dangerous. But they dont. The reasons why they dont, and why the environment has not been ruined, have to do with prices, technological innovation, social chan
31、ge and government regulation in response to popular pressure. That is why todays environmental problems in the poor countries ought, in principle, to be solvable. Raw materials have not run out, and show no sign of doing so. Logically, one day they must: the planet is a finite place. Yet it is also
32、very big, and man is very ingenious. What has happened is that every time a material seems to be running short, the price has risen and, in response, people have looked for new sources of supply, tried to find ways to use less of the material, or looked for a new substitute. For this reason prices f
33、or energy and for minerals have fallen in real terms during the century. The same is true for food. Prices fluctuate, in response to harvests, natural disasters and political instability; and when they rise, it takes some time before new sources of supply become available. But they always do, assist
34、ed by new farming and crop technology. The long-term trend has been downwards. It is where prices and markets do not operate properly that this benign (良性的 ) trend begins to stumble, and the genuine problems arise. Markets cannot always keep the environment healthy. If no one owns the resource conce
35、rned, no one has an interest in conserving it or fostering it: fish is the best example of this. 11 According to the author, most students_. （ A） believe the worlds environment is in an undesirable condition （ B） agree that the environment of the world is not as bad as it is thought to be （ C） get h
36、igh marks for their good knowledge of the worlds environment （ D） appear somewhat unconcerned about the state of the worlds environment 12 The huge increase in world production and population _. （ A） has made the world a worse place to live in （ B） has had a positive influence on the environment （ C
37、） has not significantly affected the environment （ D） has made the world a dangerous place to live in 13 One of the reasons why the long-term trend of prices has been downwards is that _. （ A） technological innovation can promote social stability （ B） political instability will cause consumption to
38、drop （ C） new farming and crop technology can lead to overproduction （ D） new sources are always becoming available 14 Fish resources are diminishing because _. （ A） no new substitutes can be found in large quantities （ B） they are not owned by any particular entity （ C） improper methods of fishing
39、have ruined the fishing grounds （ D） water pollution is extremely serious 15 The primary solution to environmental problems is _. （ A） to allow market forces to operate properly （ B） to curb consumption of natural resources （ C） to limit the growth of the world population （ D） to avoid fluctuations
40、in prices 15 Scattered around the globe are more than 100 small regions of isolated volcanic activity known to geologists as hot spots. Unlike most of the worlds volcanoes, they are not always found at the boundaries of the great drifting plates that make up the earths surface; on the contrary, many
41、 of them lie deep in the interior of a plate. Most of the hot spots move only slowly, and in some cases the movement of the plates past them has left trails of dead volcanoes. The hot spots and their volcanic trails are milestones that mark the passage of the plates. That the plates are moving is no
42、w beyond dispute. Africa and South America, for example, are moving away from each other as new material is injected into the sea floor between them. The complementary coastlines and certain geological features that seem to span the ocean are reminders of where the two continents were once joined. T
43、he relative motion of the plates carrying these continents has been constructed in detail, but the motion of one plate with respect to another cannot readily be translated into motion with respect to the earths interior. It is not possible to determine whether both continents are moving in opposite
44、directions or whether one continent is stationary and the other is drifting away from it. Hot spots, anchored in the deeper layers of the earth, provide the measuring instruments needed to resolve the question. From an analysis of the hot-spot population it appears that the African plate is stationa
45、ry and that it has not moved during the past 30 million years. The significance of hot spots is not confined to their role as a frame of reference. It now appears that they also have an important influence on the geophysical processes that propel the plates across the globe. When a continental plate
46、 comes to rest over a hot spot, the material rising from deeper layer creates a broad dome. As the dome grows, it develops deep fissures (cracks); in at least a few cases the continent may break entirely along some of these fissures, so that the hot spot initiates the formation of a new ocean. Thus
47、just as earlier theories have explained the mobility of the continents, so hot spots may explain their mutability (inconstancy). 16 We can learn from the first paragraph that _. （ A） there are no volcanic activities on hot spots （ B） most hot spots are located in the inner part of a plate （ C） hot s
48、pots usually lie at the boundaries of drifting plates （ D） the passage of plates through hot spots will leave dead volcanoes 17 The author believes that _. （ A） the motion of the plates corresponds to that of the earths interior （ B） the geological theory about drifting plates has been proved to be
49、true （ C） the hot spots and the plates move slowly in opposite directions （ D） the movement of hot spots proves the continents are moving apart 18 That Africa and South America were once joined can be deduced from the fact that _. （ A） the two continents are still moving in opposite directions （ B） they have been found to share certain geological features （ C） the African plate has been stable for 30 million years （ D） over 100 hot spots are scattered all around the globe 19 The hot sp
