阅读下列短文，从每题所给的（A、B、C和D）四个选项中，选出最佳选项。

　　There are new findings that not enough sleep may causepeople to gain weight．Researchers say a lack of sleep can produce hormonal（激素的）changes that increase feelings of hunger．

　　In one study,researchers in the Unied States examinedinformation on more than 1000 people．The people had taken part in a long term study of sleep disorders．

　　Some people slept less than five hours a night．They had15 percent higher blood levels of a hormone called ghrelin than people who slept eight hours．And they had 15 percent less oFthe hormone leptin．Experts say ghrelin helps make peoplefeel hungry;leptin makes yon feel full．

　　The scientists say these hormona changes may be a cause of obesity（肥胖症）in Western societies．They note the combination that ________ limitation is common ________ and is widely available（可得到的）．

　　The results were not affected by how much people exercised．People who are awake longer have more time to burn energy．But the researehers say loss of sleep may increase hunger especially for high-caloie foods,so people gain weight．It seems that,for survival,the body may be designed to store more fat during times with less sleep．

　　Researchers from Stanford University in California andthe University of Wisconsin did the study．They found thatthe best amount of sleep for weight control is 7.7 hours anight．

　　The Public Library of Science published the findings inits journal Medicine．Internet users can read the full study,free of charge,at plos．org．

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阅读理解

　　Judging from recent surveys, most experts in sleep behavior agree that there is virtually an epidemic(流行病)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 back to the invention of the light bulb a century age．From diary entries and our 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, the 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 in 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 or even more to feel ideally energetic．”

　　Perhaps the most merciless robber of sleep, researchers say, is the complexity of the day．Whenever pressures from work, family, friends and community increase, many people consider sleep the least expensive item on their programme．“In our society, you’re considered dynamic if you say you need only 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．”

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　　Contrary to popular beliefs, people who sleep six to seven hours a night live longer, and those who sleep eight hours or more die 　　1　　, according to the latest study ever conducted on the subject．The 　　2　　, which tracked the sleeping habits of 1.1 million Americans for six years, 　　3　　 the advice of many sleep doctors who have long 　　4　　 that people get eight or nine hours of sleep every night．

　　“There's a(n)　　5　　 idea that people should sleep eight hours a night, which has 　　6　　 scientific basis than the gold 　　7　　 of the rainbow,”said Daniel Kripke, a professor of psychiatry at the University of California at San Diego who led the study, published in a recent 　　8　　 of the Archives(档案)of General Psychiatry．“That's an old wives' tale．”

　　The study was not 　　9　　 to answer why sleeping longer may be 　　10　　 or whether people could extend their life span by sleeping 　　11　　．

　　But Kripke said it was possible that people who slept longer 　　12　　 to suffer from short-term absence of sleeping, a condition where weaken breathing puts stress on the heart and 　　13　　．He also speculated(推测)that the need for sleep was similar to 　　14　　, where getting less than people want may be 　　15　　 for them．

　　The study quickly caused warnings and criticism(批评)，with some 　　16　　 experts saying that the main problem in America's sleep habits was deprivation(剥夺)，not sleeping too 　　17　　．

　　“None of this says sleep 　　18　　 people,”said Daniel Buysse, a University of Pittsburgh psychiatrist．

　　“You should sleep as much as you need to feel 　　19　　, alert and attentive the next day,”Buysse added,“I'm much more 　　20　　 about people shortchanging themselves on sleep than people sleeping too long．”

　　Sleeplessness produces a variety of health results that were not measured in the study, critics said．

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　　YANGON－Myanmar(缅甸)has officially accepted an offer of the United States to send humanitarian aid(人道主义援助)to the country's cyclone(飓风;暴风)victims, state radio reported Friday in a night broadcast．

　　Myanmar Deputy Foreign Minister U Kyaw Thu gave the assurance Friday, saying that the country is receiving such relief aid from any country without limit at this time according to its policy of dealing with the disaster, the report said．

　　Kyaw Thu denied rumors about Myanmar's turning down such relief materials from Western countries but accepting those from nations in good relations with Myanmar, saying that the country has never done so in this case．

　　Kyaw Thu said that well-wishers abroad may make cash donation through Myanmar embassies(使馆)stationed there, while those who like to donate relief goods may present at the Yangon International Airport and seaports．

　　According to the report, the US relief aid would arrive in Yangon in days．

　　A foreign ministry's statement said earlier on Friday that at this moment, the international community can best help the victims by donating emergency provisions such as medical supplies, food, cloth, electricity generator, and materials for emergency shelter or with financial assistance,“adding that”Myanmar will wholeheartedly welcome such course of action．

　　“The government and the people of Myanmar are grateful to the friendly nations, the United Nations, international organizations, non-governmental organizations, private individuals and others for their sympathy and generosity．”it said．

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