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Text 2 Judging from recent surveys, most experts in sleep behavior agree that there is virtually an epidemic of sleepiness in the nation. "I can’t think of a single study that hasn’t found Americans getting less sleep than they ought to," says Dr David. Even people who think they are sleeping enough would probably be better off with more rest. The beginning of our sleep-deficit crisis can be traced to the invention of the light bulb a century ago. From diary entries and other personal accounts from the 18th and 19th centuries, sleep scientists have reached the conclusion that the average person used to sleep about 9. 5 hours a night. "The best sleep habits once were forced on us, when we had nothing to do in the evening down on the farm, and it was dark." By the 1950s and 1960s, that sleep schedule had been reduced dramatically, to between 7.5 and 8 hours, and most people had to wake to an alarm clock. "People cheat on their sleep, and they don’t even realize they’re doing it," says Dr David. "They think they’re okay because they can get by on 6.5 hours, when they really need 7.5, 8 hours or even more to feel ideally vigorous." Perhaps the most merciless rubber of sleep, researchers say, is the complexity of the day. When ever pressures from work, family, friends and community mount, many people consider sleep the least expensive item on his programme. "In our society, you’re considered dynamic if you say you only need 5.5 hours’ sleep. If you’ve got to get 8.5 hours, people think you lack drive and ambition." To determine the consequences of sleep deficit, researchers have put subjects through a set of psychological and performance tests requiring them, for instance, to add columns of numbers or recall a passage read to them only minutes earlier. "We’ve found that if you’re in sleep deficit, performance suffers," says Dr David. "Short-term memory is weakened, as are abilities to make decisions and to concentrate." It can he concluded from the passage that one should sleep as many hours as necessary to ______.
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Part A You will hear 10 short dialogues. For each dialogue, there is one question and four possible answers. Choose the correct answer -- [A] ,[B] ,[C] or [D] , and mark it in your test booklet. You will have 15 seconds to answer the question and you will hear each dialogue ONLY ONCE. What do we learn from the conversation
Part A You will hear 10 short dialogues. For each dialogue, there is one question and four possible answers. Choose the correct answer -- [A] ,[B] ,[C] or [D] , and mark it in your test booklet. You will have 15 seconds to answer the question and you will hear each dialogue ONLY ONCE. Where does this conversation most probably take place
Text 3 Thousands of years ago man used handy rocks for his surgical operations. Later he used sharp bone or horn, metal knives and more recently, rubber and plastic and that was where we stuck, in surgical instrument terms, for many years. In the 1960s a new tool was developed, one which was, first of all, to be of great practical use to the armed forces and industry, but which was also, in time, to revolutionize the art and science of surgery. The tool is the laser and it is being used by more and more surgeons all over the world, for a very large number of different complaints. The word "laser" means: light amplification by stimulated emission of radiation. As we all know, light is hot, any source of light -- from the sun itself down to a humble match burning -- will give warmth. But light is usually spread out over a wide area. The light in a laser beam, however, is concentrated. This means that a light with no more power than that produced by an ordinary electric light bulb becomes intensely strong as it is concentrated to a pinpoint-sized beam. Experiments with these pinpoint beams showed researchers that different energy sources produce beams that have a particular effect on certain living cells. It is now possible for eye surgeons to operate on the back of the human eye without harming the front of the eye, simply by passing a laser beam right through the eyeball. No knives, no stitches, no unwanted damage -- a true surgical wonder. Operations which once left patients exhausted and in need of long period of recovery time now leave them feeling relaxed and comfortable. So much more difficult operations can now be tried. The rapid development of laser techniques in the past ten years has made it clear that the future is likely to be very exciting. Perhaps some cancers will be treated with laser in a way that makes surgery not only safer but also more effective. Altogether, tomorrow may see more and more information coming to light on the diseases which can be treated medically. Which of the following would be appropriate to describe the instruments for surgical operations up until 1960s
Is the woman going to take the bus
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