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}} Electric Backpack Backpacks (背包) are convenient. They can hold your books, your lunch, and a change of clothes, leaving your hands free to do other things. Someday, if you don't mind carrying a heavy load, your backpacks might also power your MP3 player, keep your cell phone running, and maybe even light your way home. Lawrence C. Rome and his colleagues from the University of Pennsylvania in Philadelphia and the Marine Biological Laboratory in Woods Hole, Mass. , have invented a backpack that makes electricity from energy produced while its wearer walks. In military actions, search-and-rescue operations, and scientific field studies, people rely increasingly on cell phones, global positioning system (GPS) receivers, night-vision (夜视镜) goggles (护目镜), another battery powered devices to get around and do their work. The backpack's electricity-generating feature could dramatically reduce the amount o{ a wearer's load now devoted to spare batteries (备用电池), report Rome and his colleagues in the Sept. 9 Science . The backpack's electricity-creating powers depend on springs used to hang a cloth pack from its metal frame. The frame sits against the wearer's back, and the whole pack moves up and clown as the person walks. Agear mechanism converts vertical movements o{ the pack to rotary motions of an electrical generator, producing up to 7.4 watts. Unexpectedly, tests showed that wearers of the new backpack alter their gaits in response to the pack's oscillations, so that they carry loads more comfortably and with less effort than they do ordinary backpacks. Because of that surprising advantage, Rome plans to commercialize both electric and non-electric versions of the backpack. The backpack could be especially useful for soldiers, scientists, mountaineers, and emergency workers who typically carry heavy backpacks. For the rest of us,power-generating backpacks could make it possible to walk, play video games, watch TV, and listen to music, all at the sametime. Electricity-generating packs aren't on the market yet, but if you do get one eventually, just make sure to look both ways before crossing thestreet !

单选题Motoring Technology 1.2 million road deaths worldwide occur each year, plus a further 50 million injuries. To reduce car crash rate, much research now is focused on safety and new fuels—though some electric vehicle and biofuel research aims at going faster. Travelling at speed has always been dangerous. One advanced area of research in motoring safety is the use of digital in-car assistants. They can ensure you don"t miss important road signs or fall asleep. Most crashes result from human and not mechanical faults. Some safety developments aim to improve your vision. Radar can spot obstacles in fog, while other technology "sees through" big vehicles blocking your view. And improvements to seat belts, pedal(脚踏) controls and tyres are making driving smoother and safer. The colour of a car has been found to be linked with safety, as have, less surprisingly, size and shape. But whatever is in the fuel tank, you don"t want a thief in the driving seat and there have been many innovations (创新). Satellite tracking and remote communications can also come into play if you crash, automatically calling for help. Accidents cause many traffic jams, but there are more subtle interplays between vehicles that can cause jams even on a clear but busy road. Such jams can be analyzed using statistical tools. Robotic drivers could be programmed to make traffic flow smoothly and will perhaps one day be everyone"s personal chauffeur (司机), but their latest efforts suggest that won"t be soon.

单选题At 90, many individuals still remain healthy and energetic. A. intelligent B. rough C. robust D. revivable

单选题The room was furnished with the simplest essentials, a bed, a chair, and a tableA. suppliedB. gatheredC. graspedD. made

单选题The company Urecommended/U that a new petrol station be built here.

单选题The latest car model {{U}}embodies{{/U}} many new improvements. A. consists of B. includes C. makes up D. marks

单选题It's a Ugorgeous/U day anyway.

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}}A Biological Clock{{/B}} Every living thing has what scientists call a biological clock that controls behavior. The biological clock tells{{U}} (51) {{/U}}when to form flowers and when the flowers should open. It tells {{U}}(52) {{/U}} when to leave the protective cocoons and fly away, and it tells animals and human beings when to eat, sleep and wake. Events outside the plant and animal {{U}}(53) {{/U}} the actions of some biological clocks. Scientists recently found, for example, that a tiny animal changes the color of its fur {{U}}(54) {{/U}} the number of hours of daylight. In the short {{U}}(55) {{/U}} of winter, its fur becomes white. The fur becomes gray brown in color in the longer hours of daylight in summer. Inner signals control other biological clocks. German scientists found that some kind of internal clock seems to order birds to begin their long migration {{U}}(56) {{/U}} twice each year. Birds {{U}}(57) {{/U}} flying become restless when it is time for the trip, {{U}}(58) {{/U}} they become calm again when the time of the flight has ended. Scientists say they are beginning to learn which {{U}}(59) {{/U}} of the brain contain biological clocks. An American researcher, Martin Moorhead, said a small group of cells near the front of the brain {{U}}(60) {{/U}} to control the timing of some of our actions. These {{U}}(61) {{/U}} tell a person when to {{U}}(62) {{/U}}, when to sleep and when to seek food. Scientists say there probably are other biological clock cells that control other body activities. Dr. Moorhead is studying {{U}}(63) {{/U}} our biological clocks affect the way we do our work. For example, most of us have great difficulty if we must often change to different work hours. {{U}} (64) {{/U}} can take many days for a human body to accept the major change in work hours. Dr. Moorhead said industrial officials should have a better understanding of biological clocks and how they affect workers. He said {{U}}(65) {{/U}} understanding could cut sickness and accidents at work and would help increase a factory's production.

单选题Our statistics show that we consume all that we are capable of producing.

单选题Explorer of the Extreme Deep Oceans cover more than two-thirds of our planet. Yet, just a small fraction of the underwater world has been unexplored. Now, Scientists at the Woods Hole Oceanographic Institution (WHOI) in Massachusetts are building an underwater vehicle that will carry explorers as deep as 6,500 meters (21,320 feet). The new machine, known as a manned submersible (潜艇) or human-operated vehicle (HOV), will replace another one named Alvin which has an amazing record of discovery, playing a key role in various important and famous undersea expeditions. Alvin has been operating for 40 years but can go down only 4,500 meters (14,784 feet). "It"s about time for an upgrade", WHOI researchers say. "Alvin was launched (发动) in 1964. Since then, Alvin has worked between 200 and 250 days a year", says Daniel Fornari, a marine geologist (地址学者) and director of the Deep Ocean Exploration Institute at WHOI. During its lifetime, Alvin has carried some 12,000 people on a total of more than 3,000 dives. "A newer, better versions of Alvin is bound to reveal even more surprises about a world that is still full of mysteries", Fornari says. It might also make the job of exploration a little easier. "We take so much for granted on land," Fornari says. "We can walk around and see with our eyes how big things are. We can see colors, special arrangements." Size-wise, the new HOV will be similar to Alvin. It"ll be about 37 feet long. The setting area inside will be a small sphere, about 8 feet wide, like Alvin. It"ll carry a pilot and two passengers. It will be just as maneuverable (机动的). In most other ways, it will give passengers more opportunities to enjoy the view, for one thing. Alvin has only three windows, the new vehicle will have five, with more overlap so that the passengers and the pilot can see the same thing. Alvin can go up and down at a rate of 30 meters every second, and its maximum speed is 2 knots (about 2.3 miles per hour), while the new vehicle will be able to ascend and descend at 44 meters per second. It"ll reach speeds of 3 knots, or 3.5 miles per hour.

单选题The army should have operated in conjunction with the fleet to raid the enemy's coast.A. togetherB. in successionC. in allianceD. in connection

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.