单选题The first navigational lights in the New World were probably lanterns hung at harbor entrances. The first lighthouse was put up by the Massachusetts Bay Colony in 1716 on Little Brewster Island at the entrance to Boston Harbor. Paid for and maintained by "light dues" levied (征收) on ships, the original beacon was blown up in 1776. Until then there were only a dozen or so true lighthouses in the colonies. Little over a century later, there were 700 lighthouses. The first eight lighthouses erected on the West Coast in the 1850s featured the same basic New England design: a Cape Cod dwelling with the tower rising from the center or standing close by. In New England and elsewhere, though, lighthouses reflected a variety of architectural styles. Since most stations in the Northeast were set up on rocky eminences (高处), enormous towers were not the rule. Some were made of stone and brick, others of wood or metal. Some stood on pilings or stilts; some were fastened to rock with iron rods. Farther south, from Maryland through the Florida Keys, the coast was low and sandy. It was often necessary to build tall towers there—massive structures like the majestic lighthouse in Cape Hatteras, North Carolina, which was lit in 1870.190 feet high, it is the tallest brick lighthouse in the country. Not withstanding differences in construction appearance, most lighthouses in America shared several features: a light, living quarters, and sometimes a bell (or, later, a foghorn). They also had something else in common: a keeper and usually the keeper"s family. The keeper"s essential task was trimming the lantern wick (灯芯) in order to maintain a steady, bright flame. The earliest keepers came from every walk of life, they were seamen, farmers, mechanics, rough mill hands and appointments were often handed out by local customs commissioners as political plums. After the administration of lighthouse was taken over in 1852 by the United States Lighthouse Board, and agency of the Treasury Department, the keeper corps gradually became highly professional.

单选题Eat to Live A meager diet may give you health and long life, but it"s not much fun—and it might not even be necessary. We may be able to hang on to most of that youthful vigor even if we don"t start to diet until old age. Stephen Spindler and his colleagues from the University of California at Riverside have found that some of an elderly mouse"s liver genes can be made to behave as they did when the mouse was young simply by limiting its food for four weeks. The genetic rejuvenation won"t reverse other damage caused by time for the mouse, but could help its liver metabolize drugs or get rid of toxins. Spindler"s team fed three mice a normal diet for their whole lives, and fed another three on half-rations. Three more mice were switched from the normal diet to half-feed for a month when they were 34 months old—equivalent to about 70 human years. The researchers checked the activity of 11,000 genes from the mouse livers, and found that 46 changed with age in the normally fed mice. The changes were associated with things like inflammation and free radical production—probably bad news for mouse health. In the mice that had dieted all their lives, 27 of those 46 genes continued to behave like young genes. But the most surprising finding was that the mice that only started dieting in old age also benefited from 70 percent of these gene changes. "This is the first indication that these effects kick in pretty quickly," says Huber Warner from the National Institute on Aging near Washington D. C. No one yet knows if calorie restriction works in people as it does in mice, but Spindler is hopeful. "There"s attracting and tempting evidence out there that it will work," he says. If it does work in people, there might be good reasons for rejuvenating the liver. As we get older, our bodies are less efficient at metabolizing drugs, for example. A brief period of time of dieting, says Spindler, could be enough to make sure a drug is effective. But Spindler isn"t sure the trade-off is worth it. "The mice get less disease, they live longer, but they"re hungry," he says. "Even seeing what a diet does, it"s still hard to go to a restaurant and say: "I can only eat half of that."" Spindler hopes we soon won"t need to diet at all. His company, Lifespan Genetics in California, is looking for drugs that have the effects of calorie restriction.

单选题Robots May Allow Surgery in Space Small robots designed by University of Nebraska researchers may allow doctors on Earth to help perform surgery on patients in space. The tiny, wheeled robots, 1 are about 3 inches tall and as wide as a lipstick case, can be slipped into small incisions (切口) and computer-controlled by surgeons in different locations. Some robots are equipped 2 cameras and lights and can send images back to surgeons and others have surgical tools attached that can be 3 remotely. "We think this is going to 4 open surgery," Dr. Dmitry Oleynikov said at a news conference. Oleynikov is a 5 in computer-assisted surgery at the University of Nebraska Medical Center in Omaha. Officials hope that NASA will teach 6 to use the robots soon enough so that surgeries could one day be performed in space. On earth, the surgeons could control the robots themselves 7 other locations. For example, the robots could enable surgeons in other places to 8 on injured soldiers on the front line. Researchers plan to seek federal regulatory 9 early next year. Tests on animals have been successful, and tests on humans in England will begin very soon. The camera-carrying robots can provide 10 of affected areas and the ones with surgical tools will be able to maneuver(操控) inside the body in ways surgeons" hands can"t. The views from the camera-carrying robots are 11 than the naked eye, because they 12 back color images that are magnified(放大). Because several robots can be inserted through one incision, they could reduce the amount and 13 of cuts needed for surgery, which would decrease recovery time. This is particularly 14 to those patients who have been debilitated(使虚弱) by long illness. Eventually, Oleynikov said, the tiny robots may enable surgeons to work without ever 15 their hands in patients" bodies. "That"s the goal," Oleynikov said. "It"s getting easier and easier. We can do even more with these devices."

单选题Unless we spend money to spot and prevent asteroids(小行星) now, one might crash into Earth and destroy life as we know it, say some scientists. Asteroids are bigger versions of the meteoroids(流星) that reace across the night sky. Most orbit the sun far from Earth and don't threaten us. But there are also thousands of asteroids whose orbits put them on a collision course with Earth. Buy $ 50 million worth of now telescopes right now. Then spend $ 10 million a year for the next 25 years to locate most of the space rocks. By the time we spot a fatal one, the scientists say, we'll have a way to change its course. Some scientists favor pushing asteroids off course with nuclear weapons. But the cost wouldn't be cheap. Is it worth it? Two things experts consider when judging any risk are: 1) How likely the event is; and 2) How bad the consequences if the event occurs. Experts think an asteroid big enough to destroy lots of life might strike Earth once every 500,000 years. Sounds pretty rare— but if one did fall, it would be the end of the world. "If we don't take care of these big asteroids, they'll take care of us," says one scientist. "It' s that simple." The cure, though, might be worse than the disease. Do we really want fleets of nuclear weapons sitting around on Earth? "The world has less to fear from doomsday(毁灭性) rocks than from a great nuclear fleet set against them," said a New York Times article.

单选题The most crucial problem any economic system faces is how to use its scarce resources.

单选题Scott seized the opportunity to present his proposal to the director.

单选题It is anticipated that this contract will considerably increase sales over the next three years.A. apparentlyB. slightlyC. greatlyD. steadily

单选题Twitter, the micro-blogging service used by tens of millions of people, went off-line last month. It blamed the trouble on a malicious programmer in Russia who was trying to shut down the account of a user in neighboring Georgia. It is astonishing the local actions of a small number of programmers can bring an entire Internet service to its knees, but that appears to have been the case. Who was responsible for the collapse of Twitter?A. All its users.B. A malicious programmer in Russia.C. A small number of programmers.D. A user in neighboring Georgia,

单选题With immense relief I stopped running.

单选题The old concerns lose importance and some of them vanish altogether.

单选题At 80, Peck was still vigorous and living in Paris.A. happyB. aloneC. busyD. energetic

单选题Could you please tell me your standards when selecting a candidate?

单选题A new system of quality control was {{U}}brought{{/U}} in to overcome the defects in the firm's products. A. invested B. introduced C. installed D. insisted

单选题下面有3篇短文，每篇短文后有5道题。请根据短文内容，为每题确定1个最佳选项。{{B}}第一篇{{/B}} Pool Watch Swimmers can drown in busy swimming pools when lifeguards fail to notice that they are in trouble. The Royal Society for the Prevention of Accidents says that on average 15 people drown in British pools each year, but many more suffer major injury after getting into difficulties. Now a French company has developed an artificial intelligence system called Poseidon that sounds the alarm when it sees someone in danger of drowning. When a swimmer sinks towards the bottom of the pool, the new system sends an alarm signal to a poolside monitoring station and a lifeguard's pager. "In trials at a pool in Ancenis, near Nantes, it saved a life within just a few months, " says Alistair MeQuade, a spokesman for its maker, Poseidon Technologies. Poseidon keeps watch through a network of underwater and overheard video cameras. AI software analyses the images to work out swimmers trajectories(轨道，轨线). To do this reliably, it has to tell the difference between a swimmer and the shadow of someone being cast onto the bottom or side of the pool. "The underwater environment is a very dynamic one, with many shadows and reflections dancing around. " says McQuade. The software does this by "projecting" a shape in its field of view onto an image of the far wall of the pool. It does the same with an image from another camera viewing the shape from a different angle. If the two projections are in the same position, the shape is identified as a shadow and is ignored. But if they are different, the shape is a swimmer and so the system follows its trajectory. To pick out potential drowning victims, anyone in the water who starts to descend slowly is added to the software's "pre-alert" list, says McQuade. Swimmers who then stay immobile on the pool bottom for 5 seconds or more are considered in danger of drowning. Poseidon double-checks that the image really is of a swimmer, not a shadow, by seeing whether it obscures the pool's floor texture when viewed from overhead. If so, it alerts the lifeguard, showing the swimmer's location on a poolside screen. The first full-scale Poseidon system will be officially opened next week at a pool in High Wycombe. Buckinghamshire. One man who is impressed with the idea is Travor Baylis, inventor of the clockwork radio. Baylis runs a company that installs swimming pools -- and he was once an underwater escapologist (表演脱身术的人)with a circus. "I say full marks to them if this works and can save lives, " he says. But he adds that any local authority spending 230,000 -- plus on a Poseidon system ought to be investing similar amounts in teaching children to swim.

单选题I had nothing to say regarding this matter.

单选题A notably short man, he plays basketball with his staff several times a week.

单选题What people often talk is their dream.A. worryB. showC. reduceD. mention

单选题He often finds fault with my work.A. criticizesB. praisesC. evaluatesD. talks about

单选题From my standpoint, this thing is just ridiculous. A．field B．point of view C．knowledge D．information

单选题 The Appearance of Woman Women, as all research suggests, are much more critical of their appearance than men—much less likely to admire what they see in the mirror. Up to 8 out of 10 women are dissatisfied with their reflection, and more than half may see a distorted image. Men looking in the mirror are more likely to be either pleased with what they see or indifferent. Research shows that men generally have a much more positive body image than women—if anything, they may tend to over-estimate their attractiveness. Some men looking in the mirror may literally not see the flaws in their appearance. Why are women so much more self-critical than men? Because women are judged on their appearance more than men, and standards of female beauty are considerably higher and more inflexible. Women are continually bombarded with images of the "ideal" face. And constant exposure to idealized images of female beauty on TV, magazines and billboards makes exceptional good looks seem normal and anything short of perfection seem abnormal and ugly. It has been estimated that young women now see more images of outstandingly beautiful women in one day than our mothers saw throughout their entire adolescence. Also, most women trying to achieve the impossible standards of female beauty have in fact become progressively more unrealistic during the last century. In 1917, the physically perfect woman was about 5 feet 4 inches tall and weighed nearly 10 stone (英石). Even 25 years ago, top models and beauty queens weighed only 8% less than the average women, now they weigh 23% less. The current media ideal for women is achievable by less than 5% of the female population—and that's just in terms of weight and size. If you want the ideal shape, face etc., it's probably more like 1%.