单选题During his lifetime he was able to accumulate quite a fortune.

单选题You have to be patient if you want to sustain your position.

单选题Not long ago, most homeowners saw their roofs as simply something to keep the rain out. Now they see them as a source of electricity. Despite the bad economy, or maybe because of it, the rooftop-solar industry is booming, as Americans become increasingly intrigued(引起兴趣) by the idea of turning their roofs into mini power plants and cutting their electric bills. In 2008,33,500 rooftop solar systems were installed in the United States, a 63 percent increase over the amount of capacity installed in 2007. In California, the solar capital of country, the increase was 95 percent. The paragraph centers on the fact thatA. roofs used to be seen as a kind of protection from rain.B. economy in the US is bad at present time.C. roofs can be used as a source of electricity.D. the rooftop-solar industry is developing fast in the US.

单选题Save Energy at Home On the average, Americans waste as much energy as two-thirds of the world"s population consumes. That is largely the 1 of driving inefficient cars, using inefficient appliances (设备), and living and working in poorly insulated (隔热) buildings. Then what can you do to 2 the situation? Buy energy-efficient products. —Buy new appliances or electronics of the highest energy-efficiency rating. New energy-efficient models may cost more initially, but have a lower operating 3 over their lifetimes. The most energy-efficient models 4 the Energy Star label, which identifies products 5 use 20-40 percent less energy than standard new products. According to the EPA (美国环境保护署), the typical American household can save about $400 per year in 6 bills with products that carry the Energy Star. Switch to compact fluorescent bulbs (荧光灯). —Change the three bulbs you use 7 in your house to compact fluorescens. Each compact fluorescent bulb will keep half a ton of CO2 out of the air 8 its lifetime. 9 , compact fluorescent bulbs last ten times as long and can save $30 per year in electricity costs. Set heating and cooling temperatures correctly. —Check thermostats (温度自动调节器) in your home to make sure they are 10 at a level that doesn"t waste energy. Turn off the lights. —Turn off lights and other electrical appliances such as televisions and radios when you"re not 11 them. Install automatic timers for lights that people in your house frequently 12 to turn them off when leaving a room. Let the sun shine in. —The cheapest and most energy-efficient light and heat source is often right outside your window. On 13 days, open blinds (百叶窗) to let the sun light your home for free. Also remember that 14 entering a room equals passive solar heating. Even on cold winter days, sun streaming into a room can raise the temperature by several 15 .

单选题From my standpoint , you know, this thing is just funny.

单选题What he said was {{U}}contrariwise{{/U}} to what we expected.

单选题The president proposed that we should bring the meeting to a close.

单选题National forests make money for the government through the sale of trees for lumber.

单选题Save Energy at Home On the average, Americans waste as much energy as two-thirds of the world"s population consumes. That"s 1 the result of driving inefficient cars, using inefficient appliances, living and working in poorly insulated buildings. Then what can you do to improve the 2 ? Buy energy-efficient products—Buy new appliances or electronics of the highest energy-efficiency rating. New energy efficient models may cost more initially, but have a lower operating 3 over their lifetimes. The most energy-efficient models 4 the Energy Star label which identifies products that use 20—40 percent less energy than standard new products. According to the EPA, the typical American household can save about $ 400 per year in 5 bills with products that carry the Energy Star. Switch to compact fluorescent bulbs(荧光灯)—Change the three bulbs you use 6 in your house to compact fluorescents. Each compact fluorescent bulb will keep half a ton of carbon dioxide out of the air over its lifetime. 7 , compact fluorescent bulbs last ten times as long and can save $ 30 per year in electricity costs. Set heating and cooling temperatures correctly—Check thermostats in your home to make sure they are 8 at a level that doesn"t waste energy. Get an electronic thermostat that will allow your furnace to heat the house to a lower temperature when you"re sleeping and return it to a more 9 temperature before you wake up. Turn off the lights. 10 lights and other electrical appliances such as televisions and radios when you"re not using them. Install automatic timers for lights that people in your house frequently forget to turn them off when 11 a room. Choose renewable energy—Many consumers can now choose their energy supplier. If you have a choice, choose an electric utility that uses renewable power 12 , such as solar, water or wind. Let the sun shine in—The cheapest and most energy—efficient light and heat source is often right outside your windows. On 13 days, open blinds to let the sun light"your home for free. Also remember that 14 entering a room equals passive solar heating. Even on cold winter days, sun streaming into a room Can raise the temperature by several 15 .

单选题It doesn"t stand to reason that he would lie.

单选题The example of the diesel engine is used in the passage to illustrate that

单选题Earth"s Inner Core Scientists have long struggled to understand what lies at the planet"s center. Direct observation of its center is impossible, so researchers must 1 to other evidence. In 1889, a German scientist detected a severe earthquake in Japan. Geophysicists concluded that shock waves 2 jolts (晃动) from one side of Earth through the center to the other side. Then in 1936, Danish geophysicist lnge Lehmann studied the waves" 3 to determine that within Earth"s core of molten (熔化了的) iron lies a solid inner core—but 4 that core was made of eluded (难倒) her. Other geophysicists quickly determined that Lehmann"s inner core was composed mostly 5 iron. Since then, Lehmann"s discovery has 6 conventional Earth science. But now scientists are challenging traditional theory with new and radical 7 . For example, Earth"s center could actually contain an "inner core within the inner core", claim Ishii and colleague Adam Dziewonski. Analyzing hundreds of thousands of earthquake wave 8 , they maintain that the inner core has at its heart a tiny, even more solid sphere (球体). This sphere "may be the oldest fossil 9 from the formation of Earth," says Dziewonski. Dziewonski and Ishii speculate that shortly 10 Earth formed around 4.8 billion years ago, a giant asteroid (小行星) smashed into the young planet and nearly melted it. But Earth"s center didn"t quite melt; it 11 mass as the planet cooled. The core within a core may be the kernel (核心) that endured. "Its presence could change our basic ideas about the 12 of the planet," Dziewonski says. Dziewonski"s idea is tame (温和的) compared to the 13 theories of independent geophysicist J. Marvin Herndon. Earth"s inner core is made not of iron, he claims, but a 14 of nickel and silicon. Herndon has a truly revolutionary notion: Within the nickel silicide (硅化物) inner core is also an "inner" inner core—an 8 km-wide ball of the element uranium. Uranium is radioactive. Herndon thinks the uranium releases heat energy as its atoms 15 fission-split and crash into one another in a chain reaction. In other words, we may live on top of a gigantic, "natural" nuclear power plant.

单选题I won't {{U}}tolerate{{/U}} that kind of behavior.

单选题{{B}}第三篇{{/B}} {{B}}Plant Gas{{/B}} Scientists have been studying natural sources of methane for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist at the Max Planck Institute for Nuclear Physics in Heidelberg, Germany. Now Keppler and his colleagues find that plants, from grasses to trees, may also be sources of the greenhouse gas. This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment. Previously, researchers had thought that it was impossible for plants to make significant mounts of the gas. They had assumed that microbes need to be in environments without oxygen to produce methane. Methane is a greenhouse gas, like carbon dioxide. Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming. In its experiments, Keppler's team used sealed chambers that contained the same concentration of oxygen that Earth's atmosphere has. They measured the amounts of methane that were released by both living plants and dried plant material, such as fallen leaves. With the dried plants, the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C. At 30 degrees C, they found, a gram of dried plant material released up to 3 nanograms of methane per hour. ( One nanogram is a billionth of a gram. ) With every 10-degree rise in temperature, the amount of methane released each hour roughly doubled. Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled when living and dead plant was exposed to sunlight. Because there was plenty of oxygen available, it's unlikely that the types of bacteria that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions. That's another strong sign that the gas came from the plants and not soil microbes. The new finding is an "interesting observation," says Jennifer Y. King, a biogeochemist at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane, they may prevent plant-produced methane from reaching the atmosphere. Field tests will be needed to assess the plant's influence, she notes.

单选题The telephone system is no longer operative .

单选题Longer Lives for Wild Elephants Most people think of zoos as safe places for animals, where struggles such as difficulty finding food and avoiding predators don't exist. Without such problems, animals in zoos should live to a ripe old age. But matter may not be true for the largest land animals on Earth. Scientists have known that elephants in zoos often suffer from poor health. They develop diseases, joint problems and behavior changes. Sometimes, they even become infertile or unable to have babies. To learn more about how captivity affects elephants, a team of international scientists compared the life spans of female elephants born in zoos with female elephants living outdoors in their native lands. Zoos keep detailed records of all the animals in their care, documenting factors such as birth dates, illnesses, weight and death. These records made it possible for the researchers to analyze 40 years of data on 800 African and Asian elephants in zoos across Europe. The scientists compared the life spans of the zoo born elephants with the life spans of thousands of female wild elephants in Africa and Asian elephants that work in logging camps, over approximately the same time period. The team found that female African elephants born in zoos lived an average of 16.9 years. Their wild counterparts who died of natural causes lived an average of 56 years--more than three times as long. Female Asian elephants followed a similar pattern. In zoos, they lived 18.9 years, while those in the logging camps lived 41.7 years. Scientists don't yet know why wild elephants seem to fare so much better than their zoo-raised counterparts. Georgia Mason, a biologist at the University of Guelph in Canada who led the study, thinks stress and obesity may be to blame. Zoo elephants don't get the same kind of exercise they would in the wild, and most are very fat. Elephant social lives are also much different in zoos than in the wild, where they live in large herds and family groups. Another finding from the study showed that Asian elephants born in zoos were more likely to die earlier than Asian elephants captured in the wild and brought to zoos. Mason suggests stress in the mothers in zoos might cause them to have babies that are less likely to survive. The study raises some questions about acquiring more elephants to keep in zoos. While some threatened and endangered species living in zoos reproduce successfully and maintain healthy populations, which doesn't appear to be the case with elephants." Currently, zoos alert consumers of elephants, not net producers," Mason says.

单选题Before you decide on a vocation. it might be a good idea to consult a few good friends.A. careerB. holidayC. planD. research

单选题{{B}}第二篇{{/B}} Most of the pioneers of low-temperature physics expected gases to liquefy, but none of them predicted superconductivity. This phenomenon was discovered in 1911 by Onnes while he was studying frozen mercury. More than 40 years passed before physicists were able to offer an explanation for superconductivity. The accepted theory, developed in the 1950s, holds that the fundamental behavior of electrons changes at very low temperatures because of the effects of quantum mechanics. Electrons are tiny particles that make up the outer part of an atom, circling rapidly around the nucleus of the atom. In a regular conductor—a metal that conducts an electric current—the outermost electrons are not bound tightly to the atoms, and so they move around relatively freely. The flow of these electrons is an electric current. At normal temperatures, a conductor's electrons cannot move completely freely through the metal because they are "bumped around" by the metal's atoms. But according to the leading theory of superconductivity, when a metal is very cold, electrons form pairs. Then, like couples maneuvering on a crowded dance floor but never colliding, the paired electrons are able to move unimpeded through the metal. In pairing up, it seems, the electrons are able to "blend together" and move in unison without resistance. This explanation seems to account for superconductivity at extremely low temperatures, but in 1986 scientists in Switzerland found that some metal-containing ceramics are superconductors at much higher temperatures. By 1992, scientists had developed ceramics that become superconducting at - 297'F, and some researchers speculated that room-temperature superconductors may be possible. Scientists are still trying to formulate a theory for high-temperature superconductivity. The new ceramic materials can be maintained at their superconducting temperatures, with relatively inexpensive liquid nitrogen rather than the much colder and much more costly liquid helium required by metal superconductors. The cost difference could make superconductivity practical for many new technologies. For example, magnetically levitated trains, which require superconducting electromagnets, would be much cheaper to build than they are now. Superconducting devices might also be used for advanced power transmission lines and in new types of compact, ultrafast computers. But for the time being, superconductivity is finding application mostly in scientific research and in some kinds of medical imaging devices.

单选题Moderate Earthquake Strikes England A moderate earthquake struck parts of southeast England on 28 April 2007, toppling chimneys from houses and rousing residents from their beds. Several thousand people were left without power in Kent County. One woman suffered minor head and neck injuries. "It felt as if the whole house was being slid across like a fun-fair ride," said the woman. The British Geological Survey said the 4.3-magnitude quake struck at 8:19 a.m. and was centered under the English Channel, about 8.5 miles south of Dover and near the entrance to the Channel Tunnel. Witnesses said cracks appeared in walls and chimneys collapsed across the county. Residents said the tremor had lasted for about 10 to 15 seconds. "I was lying in bed and it felt as if someone had just got up from bed next to me," said Hedrick van Eck, 27, of Canterbury about 60 miles southeast of London. "I then heard the sound of cracking, and it was getting heavier and heavier. It felt as if someone was at the end of my bed hopping up and down." There are thousands of moderate quakes on this scale around the world each year, but they are rare in Britain. The April 28 quake was the strongest in Britain since 2002 when a 4.8-magnitude quake struck the central England city of Birmingham. The country"s strongest earthquake took place in the North Sea in 1931, measuring 6.1 on the Richter scale. British Geological Survey scientist Roger Musson said the quake took place on 28 April in an area that had seen several of the biggest earthquakes ever to strike Britain, including one in 1580 that caused damage in London and was felt in France. Musson predicted that it was only a matter of time before another earthquake struck this part of England. However, people should not be scared too much by this prediction, Musson said, as the modern earthquake warning system of Britain should be able to detect a forthcoming quake and announce it several hours before it takes place. This would allow time for people to evacuate and reduce damage to the minimum.

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. /