单选题The manager allocates duties to the clerks.

单选题The book provides a concise analysis of the country"s history.

单选题On the fourth of July 1776 the Declaration of Independence was adopted by the Continental Congress.

单选题The April edition (covering copies, overseas deliveries and office cleaning) is now available.A. recoveringB. tellingC. cuttingD. dealing with

单选题In-line Skating and Injuries An increasing number of children are taking up in-line skating, and it is those new skaters who are most at risk for injuries, according to a statement from an American research institute. Some 17.7 million people younger than age 18 participated in the sport in the US in 1996, a 24% increase over the previous year. Also in 1996, in-line skating injuries sent 76,000 skaters under the age of 21 to the emergency room. Inexperienced skaters accounted for 14% of all injuries requiring treatment. The most common reasons for injuries were losing one's balance due to road debris, being unable to stop, out-of-control speeding, or falls while doing a trick. One third of skating injuries are to the wrist, and two thirds of wrist injuries are fractures. Wearing wrist guards could reduce the number of these injuries by an estimated 87%, according to the AAP. Likewise, elbow pads could reduce elbow injuries by 82%, and knee pads could reduce the number of knee injuries by 32%, advise the experts. Helmet used by young skaters is required by law in New York and Oregon, and the research institute also recommends that young skaters wear a bicycle helmet or a similar approved sports helmet. The age at which children are ready to use in-line skates depends upon a number of conditions, including the child's foot size and body strength, general athletic ability and muscle coordination, and the ability to judge traffic and pay attention to the condition of the skating surface ahead, the experts advise. The most dangerous skating practice, called "truck-surfing", involves skating while holding onto a moving vehicle. Few skaters have fatal injuries, but 31 out of 36 deaths reported since 1992 involved being knocked down by a motor vehicle, according to data from the US Consumer Product Safety Commission.

单选题Once this profile is thoroughly drawn, you can begin to think about setting health priorities based on your particular portrait. For example, if you drink two martinis every evening, have a high - stress job, are overweight, smoke a pack of cigarettes a day, and use marijuana occasionally on weekends, you should quit smoking first, followed by losing the excess weight, reducing the stress of your job, giving up your marijuana habit, and then finally giving some thought to those martinis if you want to prevent first cancer, and then heart disease. Even for the youthful working person who has never been sick a day in his life, who is in excellent health, a good look at all health habits and at work and home environments may suggest changes that will benefi thim in the future. "Setting health priorities" in the first sentence refers toA. deciding the order of things one should do according to their impact on health.B. deciding which habit is the most important for good health.C. thinking about the impacts on health of different habits both at work and home.D. thinking about the possibility of discarding the habits bad for healt

单选题America"s emphasis on the importance of education for everyone has spurred scientific research.

单选题My father is a Uphysician/U.

单选题By conducting experiments on brave volunteers, Walter Reed was able to identify the particular kind of mosquito that carried yellow fever.

单选题{{B}}第二篇{{/B}} We all age at different rates. Heredity clearly plays an important part. But recent research studies by gerontologists indicate that life-style may be equally significant in determining who will remain youthful. As a rule, single men and women have shorter lives than married men and women. Studies show that those who have been widowed, especially men, have a longer life expectancy if they remarry soon. Both men and women seem to have a greater resistance to disease and death when their marriage is undamaged. According to a 1960 study, women who have borne three children have the lowest mortality rates. Those who have borne four or more have the highest. Childless women and those with only one child generally don't live as long as mother of two or three, according to University of Chicago sociologists Evenly M. Kitagawa and Philip M. Hauser. It's impossible to say how much sleep is ideal. Some people thrive on five hours a night, others seem to require eight or nine. Scientists agree that consistency in sleeping pattern is more significant; it's better to get six hours' sleep every night than ten hours one night and three the next. While it's true that very few people who enjoy a long life are fat, this does not mean that every pound you gain is going to shorten your life. In fact, an ongoing study in Framingham, Mass. , has showed that during at least 30 years of middle life, leanness was a higher factor for mortality than fatness! What is known is that weight extremes in either direction are definitely unhealthy. Weighing 20 percent more or less than you should weigh can, in certain cases, be a life shortener. The benefits of regular exercise are indisputable. Men engaged in energetic and persistent physical labor have fewer heart attacks. But many researchers believe that exercise need not be very strong to keep you in shape. The first principle of any life-extension program, then, is to enjoy every moment of the life you have—whether it lasts one more year or a hundred. As the philosopher Jean Jacques Rousseau put it: "Teach him to live rather than to avoid death. Life is not breath but action, the use of our senses, mind, faculties, every part of ourselves which makes us conscious of our being. "

单选题Here you can see the food compactly stored in a pressurized tank.

单选题Her sister urged her to apply for the job.

单选题 Mysterious Nazca Drawings One of the most mysterious archaeological spectacles in the world is the immense complex of geometrical symbols, giant ground-drawings of birds and animals, and hundreds of long, ruler-straight lines, some right across mountains, which stretch over 1,200 square miles of the Peruvian tablelands, at Nazca. Nazca was first revealed to modern eyes in 1926 when three explorers looked down on the desert from a hillside at dusk and briefly saw a Nazca line highlighted by the rays of the sun. But it was not until the Peruvian airforce took aerial photographs in the 1940s that the full magnificence of the panorama was apparent. Hundreds of what looked like landing strips for aircraft were revealed. There were eighteen bird-like drawings, up to 400 feet long; four-sided figures with two lines 'parallel; and long needle-like triangles which ran for miles. Among the many abstract patterns were a giant spider, a monkey, a shark, all drawn on the ground on a huge scale. The scale is monumental, but from the ground almost invisible and totally incomprehensible. The amazing fact about Nazca, created more than 1,500 years ago, is that it can only be appreciated if seen from the air. Many, therefore, regarded it as a prehistoric landing ground for visitors from outer space, but Jim Woodman, an American explorer, who was long fascinated by the mystery of Nazca, had a different opinion. He believed that Nazca only made sense if the people who had designed and made these vast drawings on the ground could actually see them, and that led him to the theory that the ancient Peruvians had somehow learned to fly, as only from above could they really see the extent of their handiwork. With this theory in mind, he researched into ancient Peruvian legends about flight and came to the conclusion that the only feasible answer was a hot-air balloon. To prove his theory, Woodman would have to make such a thing using the same fabrics and fibers that would have been available to the men of Nazca at the time. He started by gathering information from ancient paintings, legends, books and archaeological sites. After many attempts, Woodman built a balloon-type airship. It took him into the air, letting him have the sensation he had never had from viewing the same ground that he had seen many times. His flight was a modern demonstration of an ancient possibility.

单选题College Night Owls Have Lower Grades College students who are morning people tend to get better grades than those who are night owls (晚睡的人), according to University of North Texas researchers. They had 824 undergraduate (大学本科生的) students complete a health survey that included questions about sleep habits and daytime functioning, and found that students who are morning people had higher grade point averages (GPAs) than those who are night people. "The finding that college students who are evening types have lower GPAs is a very important finding, sure to make its way into undergraduate psychology texts in the near future, along with the research showing that memory is improved by sleep," study co-author Daniel J. Taylor said in a prepared statement. "Further, these results suggest that it might be possible to improve academic performance by using chronotherapy (时间疗法)to help students retrain their biological clock to become more morning types," Taylor said. The research was expected to be presented Monday at SLEEP, the annual meeting of the Associated Professional (专业的) Sleep Societies, in Baltimore. In other findings expected to be heard at the meeting, University of Colorado researchers found a significant association between insomnia (失眠) and a decline in college students" academic performance. The study included 64 psychology, nursing and medical students, average age 27.4 years, who were divided into two groups—low CPAs and high CPAs. Among those with low CPAs,69.7 percent had trouble falling asleep,53.1 percent experienced leg kicks or twitches (痉挛) at night,65.6 percent reported waking at night and having trouble falling back to sleep, and 72.7 percent had difficulty concentrating during the day. "In college students, the complaint of difficulty concentrating during the day continues to have a considerable impact on their ability to succeed in the classroom," study author Dr. James F. Pagel said in a prepared statement. "This study showed that disordered sleep has significant harmful effects on a student"s academic performance, including GPAs."

单选题Dangers Await Babies with Altitude Women who live in the world"s highest communities tend to give birth to underweight babies, a new study suggests. These babies may grow into adults with a high risk of heart disease and strokes. Research has hinted that newborns in mountain communities are lighter than average. But it wasn"t clear whether this is due to reduced oxygen levels at high altitude or because their mothers are under-nourished—many people who live at high altitudes are relatively poor compared with those living lower down. To find out more, Dino Giussani and his team at Cambridge University studied the records of 400 births in Bolivia during 1997 and 1998. The babies were born in both rich and poor areas of two cities: La Paz and Santa Cruz. La Paz is the highest city in the world, at 3.65 kilometers above sea level, while Santa Cruz is much lower, at 0.44 kilometers. Sure enough, Giussani found that the average birthweight of babies in La Paz was significantly lower than in Santa Cruz. This was true in both high and low-income families. Even babies born to poor families in Santa Cruz were heavier on average than babies born to wealthy families in lofty La Paz. "We were very surprised by this result," says Giussani. The results suggest that babies born at high altitude are deprived of oxygen before birth. "This may trigger the release or suppression of hormones that regulate growth of the unborn child," says Giussani. His team also found that high-altitude babies tended to have relatively larger heads compared with their bodies. This is probably because a fetus starved of oxygen will send oxygenated blood to the brain in preference to the rest of the body. Giussani wants to find out if such babies have a higher risk of disease in later life. People born in La Paz might be prone to heart trouble in adulthood, for example. Low birthweight is a risk factor for coronary heart disease. And newborns with a high ratio of head size to body weight are often predisposed to high blood pres- sure and strokes in later life.

单选题We are going to have the TV fixed .

单选题The most widely seen sculptural work done by Augusta Savage was probably "Lift Every Voice and Sing" , shown at the 1939-1940 New York world's fair.A. viewedB. paintedC. circulatedD. discussed

单选题 阅读下面的短文，文中有15处空白，每处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。 {{B}}Exercise Cuts Cancer Deaths in Men{{/B}} Men who exercise often are less likely to die from cancer than those who{{U}} (51) {{/U}}new research published in the British Journal of Cancer revealed yesterday. A team of scientists from the Karolinska Institute in Sweden looked{{U}} (52) {{/U}}the effect of physical activity and cancer risk in 40,708 men{{U}} (53) {{/U}}between 45 and 79. The seven-year study found that men{{U}} (54) {{/U}}walked or cycled for at least 30 minutes a day had a 34 per cent lower risk of{{U}} (55) {{/U}}from cancer than the men who did less exercise or nothing at all. {{U}}(56) {{/U}}the period studied, 3,714 men developed cancer and 1,153 died from the disease. The researchers suggest that half an hour's walking{{U}} (57) {{/U}}cycling a day increased survival among these men by 33 per cent. The researchers surveyed men from two counties in central Sweden about their lifestyle and the amount of{{U}} (58) {{/U}}activity they were usually doing. They then scored these responses and compared the results{{U}} (59) {{/U}}data on cancer diagnosis and death officially recorded in a central cancer registry over a seven-year period. Lead author, Professor Alicja Wolk, said: "These results clearly show for the first time the effect that very simple and basic daily{{U}} (60) {{/U}}such as walking or cycling has in reducing cancer death risk in middle-aged and elderly{{U}} (61) {{/U}}". Dr Lesley Walker, director of cancer information at Cancer Research UK, said: "This study gives us a clear indication that men who exercise are less{{U}} (62) {{/U}}to die from cancer, and that they are more likely to{{U}} (63) {{/U}}the disease if they get it. It's not entirely clear from this study what role exercise plays in preventing{{U}} (64) {{/U}}in men, but we do know that a healthy lifestyle can prevent up to half of all cancers — and{{U}} (65) {{/U}}exercise forms a key part of this."

单选题 Shark Attack! Craig Rogers was sitting on his surfboard, scanning the distance for his next wave, when his board suddenly stopped moving. He looked down and was terrified to see a great white shark biting the front of his board. "I could have touched its eye with my elbow," says Craig. The shark had surfaced so quietly that he hadn't heard a thing. In his horror and confusion, he waved his arms and accidentally cut two of his fingers on the shark's teeth. He then slid off the opposite side of his surfboard into the water. Then, with Craig in the water and blood flowing from his fingers, the five-meter-long shark simply swam away, disappearing into the water below. Although sharks are often categorized as killers that hunt and eat as many humans as they can, this is factually inaccurate. Sharks very rarely kill humans. A person has a greater chance of being struck by lightning or drowning in a bath than of being killed by a shark. Only 74 people have been reported killed by great whites in the last century. But great white sharks can reach six meters in length and weigh 2,200 kilograms or more. With frightening jaws that can hold up to 3,000 teeth arranged in several rows, they could very easily kill and eat a helpless human in the water. Why is it, then, that most people survive attacks by great whites? Shark researchers are trying to comprehend the reasons that allow people to escape without being eaten. The most common explanation is that great whites don't see well. It has been thought that they mistake people for the seals or sea lions which make up a large part of their diet. There is reason to doubt this, however. Recent information shows that great whites can actually see very well. Also, when attacking seals, great whites shoot up to the surface and bite with great force. When approaching humans, however, they most often move in slowly and bite less hard. They soon discover that humans are not a high-fat meal. "They spit us out because we're too bony," says Aidan Martin, director of Reef Quest Center for Shark Research. Shark researchers like Martin hypothesize that great whites are actually curious animals that like to investigate things. It's possible that they use their bite not only to kill and eat, but also to gather information. Although such an experience is unlucky for people like Craig Rogers, when sharks bite surfboards or other objects or people, they are likely just trying to learn what they are.

单选题People who eat breakfast are seldom in a bad mood．