单选题{{B}}Part A{{/B}} Read the following texts and answer the questions which accompany them by choosing A, B, C or D. Mark your answers on ANSWER SHEET 1. Text 1 "She was America's princess as much as she was Britain's princess," wrote the foreign editor of the normally sharp Chicago Tribune a week after the death in Paris of Diana, Princess of Wales. He was not far off the mark. For Americans have indeed taken posthumous possession of Britain's "People's Princess". What was happening? How was it that a nation whose school children are taught in history class to look down on the "tyranny" of the English monarchy, suddenly appeared so supportive of a member of the British royal family? Why was it that numerous American commentators sought to expand into touch the rumour that Diana had planned to move to the United States to live? Part of the answer lies in America's status as the celebrity culture par excellence. It is from their celebrities that many Americans derive their sense of nationhood. Their presidents must be celebrities in order to be elected. Writer and commentator Norman Mailer made the point after the last presidential election that Bill Clinton won because he projected the image of a Hollywood star, while Bob Dole lost because he came across as a supporting actor. What seems to have happened is that the inhabitants of the nation that produced Marilyn Monroe and Elvis Presley have found it almost impossible to accept that Princess Diana, the world's biggest, classiest contemporary celebrity by far, should have come from another country. Even that, many seemed to say to themselves, was merely an accident of birth; because in many ways she was so American. Her New Age preferences — the astrologers, the psychics, the aromatherapy — were closer to the style of former US First Lady Nancy Reagan than the House of Windsor. Her dieting and her visits to the gym were lifestyle options that were typically American. Her famous TV confession of adultery and her (purportedly unauthorized) tellall biography were also hallmarks of the American celebrity approach. Like another former First Lady, Jackie Kennedy, she auctioned her dresses — not in London or Paris, but New York. She visited America frequently and felt right at home there, revelling in the generous attentions of the rich and famous and delighting in the unreserved responsiveness of the public to her charms. For she seemed to have adapted brilliantly to another American invention: image manipulation, which all aspirants top olitical office in the US struggle to learn but which she appeared to have absorbed and refined naturally. She was, in short, a thoroughly modem woman and, like it or not, most of what is modern originates in the United States. But many Americans felt she also had more enduring qualities. Many viewed her as the incarnation of their country's dominant myth. As an editorial in the Miami Herald put it: "She was an American dream, a superstar Cinderella with the polish of a natural-born socialite ... In a way she fulfilled the American dream: to emerge from insignificance and overcome hardship and make something of herself." Elaine Showalter, a student of American popular culture who teaches English at Princet on University, noted the difference between the dullness of Prince Charles and Diana's "very American sensibility". "We have a sense here in America that anything is possible, that you are not a predetermined person; that if you are a woman from whom nothing is expected but you want to make your life count, you can do it. She shared that spirit and that's why she appealed so much to Americans."

单选题Questions 4～6 are based on the following talk; listen and choose the best answer.

单选题"Opinion" is a word that is often used carelessly today, It is used to refer to matters of taste, belief, anti judgment. This casual use would probably cause little confusion if people didn't attach too much importance to opinion. Unfortunately, most do attach great importance to it. "I have as much right to my opinion as you to yours," and "Everyone's entitled lo his opinion," are common expressions. In fact, anyone who would challenge another's opinion is likely to be branded intolerant. Is that label accurate? Is it intolerant to challenge another's opinion? It depends on what definition of opinion you have in mind. For example, you may ask a friend "What do you think of the new Buicks? "And he may reply, "In my opinion, they're ugly. "In this case, it would not only be intolerant to challenge his statement, but foolish. For it's obvious that by opinion he means his personal preference a matter of taste. And as the old saying goes, "It's pointless to argue about matters of taste. " But consider this very different use of the term. A newspaper reports that the Supreme Court has delivered its opinion in a controversial case. Obviously the justices did not stale their personal preferences, their mere likes and dislikes. They stated their considered judgment, painstakingly arrived at after thorough inquiry and deliberation. Most of what is referred to as opinion falls somewhere between these two extremes. It is not an expression of taste. Nor is it careful judgment. Yet it may contain elements of both. It is a view or belief more or less casually arrived at, with or without examining the evidence. Is everyone entitled to his opinion? Of course. In a free country this is not only permitted, but guaranteed. In Great Britain, for example, there is still a Flat Earth Society. As the name implies, the members of this organization believe that the earth is not spherical, but flat. In this country, too, each of us is free to take as creative a position as we please about any matter we choose. When the telephone operator announces That 11 be 95 ￠ for the first three minutes, you may respond "No, it won't—it'll be 28 ￠. "When the service station attendant notifies you "Your oil is down a quart, " you may reply " Wrong—it's up three. Being free to hold an opinion anti express it does not, of course, guarantee you favorable consequences. The operator may hang up on you. The service station attendant may threaten you with violence. Acting on our opinions carries even less assurance. Some time ago in California a couple took their eleven-year-old diabetic son to a faith healer. Secure in their opinion that the man had cured the boy, they threw away his insulin. Three days later the boy died. They remained unshaken in their belief, expressing the opinion that God would raise the boy from the dead. The police arrested them, charging them with manslaughter. The law in such matters is both clear and reasonable. We are free to act on our opinions only so long as, in doing so we do not harm others.

单选题It is a matter worthy of consideration, that the accounts of similar phenomena of culture, recurring in different parts of the world, actually supply incidental proof of their own authenticity. Some years since, a question which brings out this point was put to me by a great historian: "How can a statement as to customs, myths, beliefs, etc., of a savage tribe be treated as evidence where it depends on the testimony of some traveler or missionary, who may be a superficial observer, more or less ignorant of the native language, a careless retailer of unfiltered talk, a man prejudiced or even willfully deceitful?" This question is, indeed, one which we ought to keep clearly and constantly in mind. Of course we are bound to use our best judgment as to the reliability of all authors we quote, and if possible to obtain several accounts to certify each point in each locality. But it is over and above these measures of precaution that the test of recurrence comes in. If two independent visitors to different countries, say a medieval Mohammedan in Tarytary and a modern Englishman in Dahome, or a Jesuit missionary in Brazil and a Wesleyan in the Fiji Islands, agree in describing some analogous art or rite or myth among the people they have visited, it becomes difficult or impossible to set down such correspondence to accident or willful fraud. A story by someone who lived in the bush of Australia may, perhaps, be objected to as a mistake or an invention, but did a Methodist minister in Guinea conspire with him to cheat the public by telling the same story there? The possibility of intentional or unintentional mystification is often barred by such a state of things as that a similar statement is made in two remote lands, by.two witnesses, of whom A lived a century before B, and B appears never to have heard of A. How distant are the countries, how wide apart the dates, how different the creeds and characters of the observers, in the catalogue of facts of civilisation, needs no farther showing to any one who will even glance at the footnotes of the present work. And the more odd the statement, the less likely that several people in several places should have made it wrongly. This being so, it seems reasonable to judge that the statements are in the main truly given, and that their close and regular coincidence is due to the accidental occurrence of similar facts in various districts of culture.

单选题On July 4, 1776, a secret meeting of insurgent colonists in America passed the Declaration of Independence. War against the British had already been going on for over a year, so the declaration came as the climax of years" stormy events in America. The impetus for the American Revolution was the treaty of Paris in 176a, which ended the struggle between the British and French for control over North America. Since the colonists no longer were frightened by the French, they ceased to rely upon the British for protection and were not as submissive as they were formerly. On the other hand, the British regarded the colonies as a source of revenue and began to impose unfair taxes upon them. The Sugar Act in 1764 and the Stamp Act in 1765 were so eagerly opposed by discontented colonists that rioting broke out. The Stamp Act was repealed in 1776 as a result of the riots. The British continued their policy of taxation without collaboration with their once obedient subjects. The Townshend Acts (a series of taxes on glass, lead, paper, and tea) created such disgust that the citizens of Boston attacked British soldiers who fired upon them. A new tea tax in 177a again consolidated Boston residents" disagreement. About fifty men disguised as Indians boarded British ships and got rid of their cargo of tea in protest against the tea tax. That was the famous Boston Tea Party. In reprisal, the British abolished the Bostonians" right to self-rule, and by passing what were referred to as Intolerable Acts in Boston, they infuriated all of the colonies and caused them to unite in protest. Representatives from twelve colonies gathered in Philadelphia in 1774 to plan a stratagem to avoid British interference in trade and to protest the infamy of taxation without representation. The British responded that the colonies were in rebellion, and, since nothing would soothe either side, both sides prepared for war.

单选题I lost my sight when I was four years old by falling off a box car in a freight yard in Atlantic City and landing on my head. Now I am thirty two. I can vaguely remember the brightness of sunshine and what color red is. It would be wonderful to see again, but a calamity can do strange things to people. It occurred to me the other day that I might not have come to love life as I do if I hadn't been blind. I believe in life now. I am not so sure that I would have believed in it so deeply, otherwise. I don't mean that I would prefer to go without my eyes. I simply mean that the loss of them made me appreciate the more what I had left. Life, I believe, asks a continuous series of adjustments to reality. The more readily a person is able to make these adjustments, the more meaningful his own private world becomes. The adjustment is never easy. I was bewildered and afraid. But I was lucky. My parents and my teachers saw something in me—a potential to live, you might call it—which I didn't see, and they made me want to fight it out with blindness. The hardest lesson I had to learn was to believe in myself. That was basic. If I hadn't been able to do that, I would have collapsed and become a chair rocker on the front porch for the rest of my life. When I say belief in myself I am not talking about simply the kind of self confidence that helps me down an unfamiliar staircase alone. That is part of it. But I mean something bigger than that. an assurance that I am, despite imperfections, a real, positive person; that somewhere in the sweeping, intricate pattern of people there is a special place where I can make myself fit. It took me years to discover and strengthen this assurance. It had to start with the most elementary things. Once a man gave me an indoor baseball. I thought he was mocking me and I was hurt. "I can't use this. " I said. "Take it with you," he urged me, "and roll it around. " The words stuck in my head. "Roll it around!" By rolling the ball I could hear where it went. This gave me an idea how to achieve a goal I had thought impossible.. playing baseball. At Philadelphia's Overbrook School for the Blind I invented a successful variation of baseball. We called it ground ball. All my life I have set ahead of me a series of goals and then tried to reach them, one at a time. I had to learn my limitations. It was no good to try for something I knew at the start. It was wildly out of reach because that only invited the bitterness of failure. I would fail sometimes anyway but on the average I made progress.

单选题WhatkindofanimalsisAnnaaskedtolookafter?A.Rabbits.B.Birds.C.Cats.D.Dogs.

单选题The modem world only recently reached the Yanomamo, a native people of the Amazon basin. Sheltered by thick rainforest, the Yanomano lived a self-contained existence until gold was discovered in their jungle homeland. Miners flocked into the forests, cutting down trees and bringing in disease and shot those Yanomamo who would not get out of the way. In just seven years from the early 1980s, the population fell 20 percent. Hands Around the World, a native American cultural association, says the Yanomamo are believed to be the most culturally intact people in the world. They wear loin cloths, use fire sticks and decorate their bodies with dye from a red berry (浆果). They don't use the wheel and the only metal they use is what has been traded to them by outsiders. When a Yanomamo dies, the body is burned and the remaining bones crushed into a powder and turned into a drink that is later consumed by mourners in memory of the dead. A Hands Around the World report says that in South America not only are the cultures and traditions in danger of disappearing, but some tribes are in danger of extinction. "The Yanomamo is a well-known tribe that is rapidly losing its members through the destruction of Western disease," the report says. Before illegal gold miners entered their rainforest, the Yanomamo were isolated from modern society. They occupy dense jungle north of the Amazon River between Venezuela and Brazil and are catalogued by anthropologists (人类学家) as neo-indians with cultural characteristics that date back more than 8,000 years. Each community lives in a circular communal house, some of which sleep up to 400, built around a central square. Though many Yanomamo men are monogamous, it is not unusual for them to have two or more wives. Anthropologists from the University of Wisconsin say polygamy is a way to increase one's wealth because having a large family increases help with hunting and cultivating the land. These marriages result in a shortage of women for other men to marry, which has led to inter-tribal wars. Each Yanomamo man is responsible for clearing his land for gardening, using slash-and-hum farming methods. They grow plantains, a type of banana, and hunt game animals, fish and anaconda (南美热带蟒蛇) using bows and arrows.

单选题{{B}}Text 3{{/B}} People's attitude toward drugs has become to resemble an emotional roller coaster, careening wildly from dizzy heights of pharmacologic faith to gloomy terror over drug hazards. A host of dreaded killers that had tyrannized the world for centuries can now be cured. That is a cause for some to regard drugs as "miraculous". On the other hand, there are hundreds of pitifully deformed babies born of mothers who had taken thalidomide -- the very thought of them causes terror. What is the-sensible attitude toward drugs? I think the first thing to think about is the differences between drugs and wonder drugs. The antibiotics, such as penicillin, can really cure certain bacterial diseases. On the other hand, the major diseases threatening Americans today are cancer, stroke, hypertension, coronary disease, arthritis and psychoses. Against them, the doctor's bag of tricks is limited. He has no wonder drug. Of course, many patients suffering from these illnesses can be improved by taking drugs and a few can be dramatically helped. But no drug has cured a single case of schizophrenia or rheumatoid arthritis, in the way that penicillin can cure pneumonia or meningococcal meningitis. So the first important lesson is not to expect too much from drugs. Too many patients exert unholy pressures on doctors to prescribe for every symptom, even when such treatment is unwarranted or dangerous. Unfortunately, the medical profession is guilty of some complicity here The patient who demands a shot of penicillin for every sniffle and sneeze may be given the injection by a reluctant physician because he is certain that if he does not, the patient will search until he or she finds a doctor who will. More important, the physician is apt to be a willing collaborator in over-medication because he, too, has been oversold on drugs. He is rarely at a loss for a remedy that might be just what the patient needs. Doctors want their patients to get well. They also derive feelings of power and ego-satisfaction from the ability to pre- scribe the latest drugs. At the other extreme is the patient who is suspicious of all medications. In the category are the patients who never take an aspirin tablet because they believe that "every aspirin you take leaves a scar on the lining of your stomach". Without doubt, such ill-advised behavior is at times traceable to lurid accounts of drug dangers. Not long ago, when one antidepressant drug was temporarily withdrawn from the market by the Food and Drug Administration, radio and television stations in New York carried stories about that. Patients were advised by commentators not to take any medication at all. The resulting hysteria in hundreds of patients was as real as it was predictable.

单选题Questions 14～16 are based on the following conversation. You now have 15 seconds to read Questions 14～16.

单选题The electric catfish has a different electric system in that

单选题Only a man who hates himself and loves humanity could possibly become an actor, but to become an actor doing plays for live television is without doubt the most ghastly torture ever invented for the acting profession. So, at least, a well-known actor has stated and I am quite prepared to believe it. Consider for yourself. For one thing the unseen audience may number millions. If you forget your lines there is no hope whatsoever of being prompted and the only resource left to you is that of mouthing silently at the cameras in the vain hope that thousands of viewers will think that the fault is in their sets rather than that the actor is incompetent. There is a story told by a famous actor of his experiences in this field which gives me intense pleasure whenever I read it. The types of part he usually plays are generally somewhat stiff-upper-lip typically British parts. He was due to act in a live television show where the script was of indifferent quality, rehearsals had been sketchy and a great deal more attention had been paid to the trappings of the production than to its actual quality. He claims himself that acting live on television scares him stiff. However, on this occasion he was determined to give as good an impression as possible of the "stiff-upper-lip". He was acting a part where the costume was fairly simple and his idea of making a "calm and collected" impression was to leave the main items (coat, briefcase and beret) in the little hut he had been assigned as a dressing room and stroll about the stage five minutes before the performance was due to start, apparently totally unprepared. This worked beautifully. Everyone naturally, from the producer to the humblest stage-hand, begged him to get ready. "Two minutes will be quite enough," he stated calmly, puffing at an enormous cigar. Two minutes before the live show was due to start he strolled to the dressing room and tried to open the door. It was locked. He then describes himself as being changed into a gibbering nervous wreck, shouting and screaming for help. He finally went on the set with his coat on back to front and covered with woodshavings from having had to break down the door. He forgot his lines and the cool Englishman with the iron nerve he was supposed to be playing turned into, as he describes it, a furtive little man with a dirty coat, a stammer and a nervous twitch. He has now decided that live television is not for him, a fact which will hardly surprise the reader.

单选题{{B}}Part A{{/B}} Read the following texts and answer the questions which accompany them by choosing A,B , C or D. Mark your answers on ANSWER SHEET 1. {{B}}Text 1{{/B}} In recent years, there has been a steady assault on salt from the doctors: Salt is bad for you—regardless of your health. Politicians also got on board. "There is a direct relationship," US congressman Neal Smith noted, "between the amount of sodium a person consumes and heart disease, circulatory disorders, stroke and even early death. "Frightening,if true ! But many doctors and medical researchers are now beginning to feel the salt scare has gone too far. "All this hue and cry about eating salt is unnecessary," Dr. Dustan insists. "For most of us it probably doesn't make much difference how much salt we eat. " Dustan's most recent short-term study of 150 people showed that those with normal blood pressure underwent no change at all when placed on an extremely low-salt diet, or later when salt was reintroduced. Of the hypertensive subjects ,however,half of those on the low-salt diet did experience a drop in blood pressure, which returned to its previous level when salt was reintroduced."An adequate to somewhat excessive salt intake has probably saved many mote lives than it has cost in the general population," notes Dr. John H.Largh. "So a recommendation that the whole population should avoid salt makes no sense."Medical experts agree that everyone should practice reasonable "moderation" in salt consumption. For an average person, a moderate amount might run from four to ten grams a day, or roughly 1/2 to 1/3 of a teaspoon. The equivalent of one to two grams of this salt allowance would come from the natural sodium in food. The rest would be added in processing, preparation or at the table.Those with kidney, liver or heart problems may have to limit dietary salt, if their doctor advises. But even the very vocal "low salt" exponent, Dr. Arthur Hull Hayes, Jr. admits that "We do not know whether increased sodium consumption causes hypertension. " In fact, there is increasing scientific evidence that other factors may be involved: deficiencies in calcium, potassium, perhaps magnesium;obesity (much more dangerous than sodium) ;genetic predispotition; stress."It is not your enemy," says Dr. Laragh, "Salt is the No. 1 natural component of all human tissue, and the idea that you don't need it is wrong. Unless your doctor has proven that you have a salt-related health problem, there is no reason to give it up. "

单选题The role of the federal government in preventing adolescent drug use was a central issue of the 1996 presidential campaign. Bob Dole criticized the Clinton administration for reducing the staff of the Office of National Drug Control Policy while Clinton criticized attempts by the Republican majority in Congress to cut federal support of drug-prevention programs. It seemed as though everyone wanted to be seen as favoring federal spending on drug prevention, and in particular, drug education. Indeed, 65 percent of congressional candidates polled in 1996 by the Community Anti-Drug Coalitions of America ranked prevention programs as the number one priority in reducing the country's drug problem, compared to just 9 percent for both prohibition and treatment. By the close of 1996, Republicans had abandoned their attempts to reduce the federal prevention budget and Clinton had secured extra funds for drug-education programs within the Department of Health and Human Services and the Department of Education. There is no mystery in the bi-partisan popularity of such education programs. Recently completed large-scale surveys have shown that illegal drug use among young people increased in the past three years, following more than a decade of steady decline. Advocates of drug education argue that federally funded initiatives of the past 10 years contributed, at least in part, to the decline in adolescent drug taking, and that cuts in federal spending led to the recent increased use. However, unlike other aspects of drug control policy, prevention or education has been hardly analyzed. Law enforcement and prohibition efforts have been the subject of debate in both the popular press and academic circles. In contrast, prevention is simply assumed to be a praiseworthy enterprise, and the claims of its advocates are uncritically accepted by the press and policy makers. Despite claims to the contrary, available data do not support the view that the decline in adolescent drug use that occurred between the early1980s and early 1990s was influenced by the level of federal spending on drug-education activities. Indeed, if one takes into account the fact that the effects of spending do not manifest themselves in actual behavior for at least three years, then increased spending coincided with increased drug use. The massive increase in federal spending that occurred in the mid-1980s drew a lot of people and programs into the drug-prevention arena in an indiscriminate manner. A good deal of this money went to people with limited experience and expertise in drug prevention. It is thus hardly surprising that we often get more, not less, drug use as a result of these activities.

单选题It can be inferred that the author assumes that commonsense knowledge of human relations is______.

单选题 Questions 11 to 13 are based on the following interview between a reporter and a Taxi company manager about mobile phone hails u taxi. You now have 15 seconds to read Questions 11 to 13.

单选题The passage suggests that as any individual home is just a fragment of a huge communal picture when you paint your house______.

单选题Text 1 Since the dawn of human ingenuity, people have devised ever more cunning tools to cope with work that is dangerous, boring, burdensome, or just plain nasty. That compulsion has resulted in robotics — the science of conferring various human capabilities on machines. And if scientists have yet to create the mechanical version of science fiction, they have begun to come close. As a result, the modern world is increasingly populated by intelligent gizmos whose presence we barely notice but whose universal existence has removed much hum an labor. Our factories hum to the rhythm of robot assembly arms. Our banking is done at automated teller terminals that thank us with mechanical politeness for the transaction. Our subway trains are controlled by tireless robo-drivers. And thanks to the continual miniaturization of electronics and micro-mechanics, there are already robot systems that can perform some kinds of brain and bone surgery with submillimeter accuracy—far greater precision than highly skilled physicians can achieve with their hands alone. But if robots are to reach the next stage of laborsaving utility, they will have to operate with less human supervision and be able to make at least a few decisions for themselves — goals that pose a real challenge. "While we know how to tell a robot to handle a specific error," says Dave Lavery, manager of a robotics program at NASA, "we can't yet give a robot enough 'commonsense' to reliably interact with a dynamic world." Indeed the quest for true artificial intelligence has produced very mixed results. Despite a spell of initial optimism in the 1960s and 1970s when it appeared that transistor circuits and microprocessors might be able to copy the action of the human brain by the year 2010, researchers lately have begun to extend that forecast by decades if not centuries. What they found, in attempting to model thought, is that the human brain's roughly one hundred billion nerve cells are much more talented — and human perception far more complicated—than previously imagined. They have built robots that can recognize the error of a machine panel by a fraction of a millimeter in a controlled factory environment. But the human mind can glimpse a rapidly changing scene and immediately disregard the 98 percent that is irrelevant, instantaneously focusing on the monkey at the side of a winding forest road or the single suspicious face in a big crowd. The most advanced computer systems on Earth can't approach that kind of ability, and neuroscientists still don't know quite how we do it.

单选题In their darker moments, climatologists talk about their own "nightmare scenario". This is one where global warming has caused such significant climatic changes that ocean currents change direction. One scene from tile nightmare has the Gulf Stream moving south or even going into reverse, making winter in London look and feel like a St Petersburg January. The ocean is a great moderating influence on the planet, soaking up heat around the tropics and depositing it in the cooler polar regions. Yet scientists know surprisingly little about how the sea does this— they estimate that the North Atlantic alone moves energy equivalent to the output of several hundred million power stations. Last year oceanographers began their biggest international research initiative to learn more about ocean circulation. The first results from the World Ocean Circulation Experiment demonstrate just how complex the movement of sea-water can be. They have also given scientists a glance of the amount of heat being exchanged between the oceans and the atmosphere. As part of the experiment, researchers are monitoring the speed and direction of ocean currents, water temperature and salinity. Research ships taking part will gather detailed measurements at 24,000 points or "stations" along carefully designated trans-ocean routes. This undertaking dwarfs the 8,000 hydrographic stations created in the past hundred years of ocean surveying, A fleet of ships, buoys, seabed sensors and satellites will collect so much data that Britain, one of the 40 countries taking part, has opened a research institute, the James Rennell Centre for Ocean Circulation in Southampton, to process them. One of the justifications for the experiment, says John Woods, director of marine and atmospheric sciences at the Natural Environment Research Council, is that the oceans hold the key to understanding long-term changes in the global climate. The Earth has two "envelopes"—the ocean, consisting of slowly circulating water, and the atmosphere, made of fast-moving air. Far from being independent, they interact, one modifying the other until a balance is reached between them. The present balance came about at the end of the last Ice Age, about 10,000 years ago. Scientists hope that knowing more about the ocean"s "weather patterns" will help them to predict climate changes further ahead. Knowing how heat is moving around the ocean is decisive to such long-term forecasting. The top three metres of the ocean store more heat than all of the atmosphere. Some of the heat can be transported downward between 30 metres and several thousand metres. The deeper it goes, the longer it stays out of the atmosphere. Water heated in the equatorial region flows in shallow currents north or south towards the poles, where it releases its heat to the air and, as it becomes colder and denser, sinks to the sea floor, where it forms deep, cold currents that back to the equator. John Gould, one of the British scientists taking part in the ocean circulation experiment, is discovering just how this occurs in the Noah Atlantic. Shallow currents, less than 500m deep, of warm water at about 8℃ flow from the Atlantic into the Norwegian Sea, mainly along a path that follows the point where the continental shelf ends and the deep mid-ocean valleys begin. Meanwhile, at depth down to 5,000m, deep currents of cold water at about minus 1℃ flow south into the Atlantic along the deep ocean valley. (Salt water at this depth does not freeze at 0℃) Sensors positioned on the seabed have given Dr Could and his researchers an accurate assessment of just how much cold water is flowing back into the North Atlantic and have given up its heat to the atmosphere over north-west Europe. In total, he estimates, about 5 million cubic metres of water per second flows in these deep currents between Greenland and the British Isles. This means the warm water of the North Atlantic must be giving up about 200 million megawatts of energy to the atmosphere over north-west Europe. Research at the other end of the world, in the seas around Antarctica, is also finding that sea-floor topography plays a crucial role in determining the direction of ocean currents. In the past, oceanographers have assumed, for instance, that surface currents such as the Gulf Stream do not extend much beyond a kilometre in depth. But an analysis of currents in Antarctic waters has shown that currents are. not concentrated in the top kilometre, but reach down to the submerged mountain ranges. Dr Woods believes such research will help to save lives. "More deaths can be prevented by ocean forecasting, than by weather forecasting and our economic and social well-being are more vulnerable to change in the ocean than in the atmosphere."

单选题The linear flight formations of migratory birds are called echelons. The V and the J structures are typical and are the most readily recognized flock echelons, but other variations also occur. Studies of several species have shown that a true V-shaped echelon is, in fact, less common than a J formation is. There are two well-supported and complementary explanations for why birds fly in formation. One is to conserve energy by taking advantage of the upward vortex fields created by the wings of the birds in front. The other is to facilitate orientation and communication among the birds. These explanations are not mutually exclusive, and both have been backed by a variety of studies. The relative importance of each undoubtedly shifts as various factors, such as the season of the year or the purpose of individual flights, change. During local feeding flights, for example, energy conservation is probably much less important than careful orientation and collision avoidance are. During long-distance migration, orientation and communication remain necessary, but there is also much to be gained for each bird in the flock by optimizing its position to conserve energy. Fluid dynamics and energy wave configuration calculations have been used to test predictions of where birds should position themselves in relation to others to conserve the most energy as they travel through the air. Analyses of flock formations using photography have measured bird positions and found them to almost always be located such that they gain some energetic advantage. The animals are not very often in the expected optimal location, however, indicating that other factors also influence position in the formation. Knowledge of birds' visual axes, "blind spots" and field of vision has allowed researchers to pinpoint the best locations for birds within a flock to maintain optimal visual positioning. Actual positions of the animals are usually positively related to these predictions but are, again, not always optimal. Studies have categorized the positions of birds and found that some individuals take positions that are most closely predicted to satisfy the energy conservation hypothesis; others are in better visual contact positions; and still others are not apparently responding to either benefit or are in a position that should gain some advantage from both benefits. The leaders of formations change from time to time, but the causes, frequency and characteristics of these changes have not yet been determined. Sustained observation from the ground of flocks covering great distances in the air is very difficult. There are plenty of intuitive predictions about leader choice that quickly come to mind relative to the age, experience, sex, condition and social status of the leaders, but researchers have not figured out how to overcome the prohibitive logistic issues to test them. Some scientists have trained birds to fly in formation with small aircraft; perhaps their experiences will yield opportunities to test these ideas.