单选题Acetate is one of the most important {{U}}artificial{{/U}} fibers.

单选题High-tech Warfare Today, high-tech warfare (战争) is no longer an abstract concept, but a real issue. Technology 1 tactics, sociology, and the development of weaponry (武器). It also causes the changes in battles. Then what are the new characteristics of modern battles 2 by the application of high technologies? High-tech warfare naturally includes high technology. In modern battles, a single kind of weapon can hardly be 3 . Various weaponry, such as intelligence detection and information processing, should 4 well with each other. Aerial (航空的) weaponry becomes the main force in battles in the sky. Precision homing (精确自导) weaponry like cruise missiles and missiles 5 satellite homing systems becomes the main attack weapons. Battle control systems play a dominant role. Various weapons and logistics (后勤) systems are 6 into a comprehensive framework, centrally representing the modern high-tech weaponry. Depending on various 7 equipment and means in electronic warfare, our army will not be passively beaten. 8 the battlefield ,high-tech warfare has created a type of non-linear (非线性的) chaos. Because of the use of long-range precision weaponry, the opposite parties in warfare can"t "touch" or "see" each other, and distance is no longer the decisive factor affecting the 9 of battles. It is hard to clearly define the lines between the frontier and the rear, as well as attack and defense. The traditional three-dimensional air-sea battlefield will be 10 by the multi-dimensional battlefield composed of air, sea, magnetic, electrical and information battlefields. No large.-scale movements can be conducted 11 . Because modern weaponry systems are closely related to chains of demand and communication and electronic technology, the parties 12 have to pay attention to the usufruct (使用权) and control of electromagnetic frequency spectrum. So electronic Warfare becomes 13 important and the necessary guarantee of victory. Whatever 14 warfare goes to and whatever cloak (宽 大外衣) it wears, it always violates peace and brings the world bloodshed (流血). Most people think of high technology as a 15 to enhance their lives, and they don"t wish it to be used to destroy lives.

单选题They have the capability to destroy the enemy in a few days.

单选题John {{U}}removed{{/U}} his overcoat.

单选题{{B}}第二篇{{/B}} {{B}} Thanksgiving Day{{/B}} The American Thanksgiving Day celebration goes back to 1621. In that year, a special dinner was prepared in Plymouth, Massachusetts. The people who had settled there had left England because they were forbidden to keep their religious belief. They came to the new land and faced difficulties in sailing across the ocean. The ship which carried them was called "the Mayflower". The North Atlantic was hard to travel. There were bad storms and huge waves. With the help of the Indians, they learned to live in the new land. These Puritans, as they were called, had much to be thankful for. They could enjoy religious freedom. They learned how to grow their crops in accordance with the climate and soil. Now when they selected the fourth Thursday of November for their Thanksgiving celebration, they invited their neighbors, the Indians, to join them in dinner. They also wanted to pray God for the new life. They recalled the group of 102 men, women and children who left England. They remembered those who did not live to see the shores of Massachusetts. They thought of the 65 day's journey which tested their strength.

单选题Computer Mouse The basic computer mouse is an amazingly clever invention with a relatively simple design that allows us to point at things on the computer and it is very productive. Think of all the things you can do with a mouse like selecting text for copying and pasting (涂), drawing, and even scrolling on the page with the newer mice with the wheel. Most of us use the computer mouse daily without stopping to think how it works until it gets dirty and we have to learn how to clean it. We learn to point at things before we learn to speak, so the mouse is a very natural pointing device. Other computer pointing devices include light pens, graphics (图形) tablets and touch screens, but the mouse is still our workhorse. The computer mouse was invented in 1964 by Douglas Englehart of Stanford University. As computer screens became more popular and arrow keys were used to move around a body of text, it became clear that a pointing device that allowed easier motion through the text and even selection of text would be very useful. The introduction of the mouse, with the Apple Lisa computer in 1983, really started the computer public on the road to relying on the mouse for routine (常规) computer tasks. How does the mouse work? We have to start at the bottom, so think upside down for now. It all starts with the mouse ball. As the mouse ball in the bottom of the mouse rolls over the mouse pad, it presses against and turns two shafts (轴). The shafts are connected to wheels with several small holes in them. The wheels have a pair of small electronic light-emitting devices called light-emitting diodes (LED) mounted on either side. One LED sends a light beam to the LED on the other side. As the wheels spin and a hole rotates by, the light beam gets through to the LED on the other side. But a moment later the light beam is blocked until the next hole is in place. The LED detects (发现) a changing pattern of light, converts the pattern into an electronic signal, and sends the signal (发信号) to the computer through wires in a cable that goes out the mouse body. This cable is the tail that helps give the mouse its name. The computer interprets the signal to tell it where to position the cursor on the computer screen. So far we have only discussed the basic computer mouse that most of you probably have or have used. One problem with this design is that the mouse gets dirty as the ball rolls over the surface and picks up dirt. Eventually you have to clean your mouse. The newer optical mice avoid this problem by having no moving parts.

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.