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Black HolesMost scientists agree that black holes exist but are nearly impossible to locate. A black hole in the universe is not a solid object, like a planet, but it is shaped like a sphere (球体). Astronomers (天文学家) think that at the center of a black hole there is a single point in space with infinite(无限的)density(稠密), This single point is called a singularity (奇点). If the singularity theory is correct, it means that when a massive star collapses, all the material in it disappears into the singularity. The center of a black hole would not really be a hole at all, but an infinitely dense point. Anything that crosses the black hole is pulled in by its great gravity.Although black holes do exist, they are difficult to observe. These are the reasons.· No light or anything else comes out of black holes. As a result, they are invisible to a telescope.· In astronomical terms, black holes are truly. For example, a black hole formed by the collapse of a giant star would have an event horizon(视界) only 18 miles across.· The nearest black holes would be dozens of light years away from Earth. One light year is about 6 trillion (万亿) miles. Even the most powerful telescopes could not pick out an object so small at such a great distance.In 1994 the Hubble Space Telescope provided evidence that black holes exist. There are still answers to be found, however, so black holes remain one of the mysteries of the universe. The Hubble Space Telescope helps scientists to understand the nature of the universe.（）
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An Intelligent CarDriving needs sharp eyes, keen ears, quick brain, and coordination(协调) between hands and the brain. Many human drivers have all (51) and can control a fast-moving ear. But how does an intelligent car control itself?There is a virtual(虚拟) driver in the smart car. This virtual driver has "eyes", "brains", "hands" and "feet" too. The minicameras (52) each side of the ear are his "eyes" which (53) the road conditions ahead of it. They watch the (54) to the car’s left and right. There is also a highly automatic driving (55) in the car. It is the built-in computer, which is the virtual driver’s "brain". His "brain" (56) the speeds of other moving cars near it and analyzes their positions. Basing on this information, it chooses the (57) path for the intelligent ear, and gives instructions to the "hands" and "feet" to act accordingly. In this way, the virtual driver (58) his car.What is the virtual driver’s best advantage He reacts (59) . The minicameras are bringing (60) continuously to the "brain". It completes the processing of the images with-in 100 milliseconds. (61) , the world’s best driver needs at least one second to react. Besides, when he takes (62) , he needs one more second.The virtual driver is really wonderful. He can reduce the accident (63) considerably on expressways(高速公路). In this (64) , can we let him have the wheel at any time and in any place Experts (65) that we cannot do that just yet. His ability to recognize things is still limited. He can now only drive an intelligent car on expressways. 64（）
An Intelligent CarDriving needs sharp eyes, keen ears, quick brain, and coordination(协调) between hands and the brain. Many human drivers have all (51) and can control a fast-moving ear. But how does an intelligent car control itself?There is a virtual(虚拟) driver in the smart car. This virtual driver has "eyes", "brains", "hands" and "feet" too. The minicameras (52) each side of the ear are his "eyes" which (53) the road conditions ahead of it. They watch the (54) to the car’s left and right. There is also a highly automatic driving (55) in the car. It is the built-in computer, which is the virtual driver’s "brain". His "brain" (56) the speeds of other moving cars near it and analyzes their positions. Basing on this information, it chooses the (57) path for the intelligent ear, and gives instructions to the "hands" and "feet" to act accordingly. In this way, the virtual driver (58) his car.What is the virtual driver’s best advantage He reacts (59) . The minicameras are bringing (60) continuously to the "brain". It completes the processing of the images with-in 100 milliseconds. (61) , the world’s best driver needs at least one second to react. Besides, when he takes (62) , he needs one more second.The virtual driver is really wonderful. He can reduce the accident (63) considerably on expressways(高速公路). In this (64) , can we let him have the wheel at any time and in any place Experts (65) that we cannot do that just yet. His ability to recognize things is still limited. He can now only drive an intelligent car on expressways. 52（）
第三篇Renewable Energy SourcesToday petroleum (石油)provides around 40% of the world’s energy needs, mostly fuelling automobiles. Coal is still used, mostly in power stations, to cover one-quarter of our energy needs, but it is the least efficient, unhealthiest and most environmentally damaging fossil fuel(矿物燃料). Natural gas reserves could fill some of the gap from oil, but reserves of that will not last into the 22nd century either. Most experts predict we will exhaust easily accessible reserves within 50 years. Less polluting renewable energy sources offer a more practical long-term energy solution. "Renewable" refers to the fact that these resources are not used faster than they can be replaced.Hydroelectric(水力发电的) power is now the most common form of renewable energy, supplying around 20% of world electricity. China’s Three Gorges Dam is the largest ever. At five times the size of the US’s Hoover Dam, its 26 turbines(涡轮机) will generate the equivalent energy of 18 coal-fired power stations. It will satisfy 3% of China’s entire electricity demand.In 2003, the first commercial power station to use tidal (潮汐的)currents in the open sea opened in Norway. It is designed like windmill (风车), but others take the form of turbines.As prices fall, wind power has become the fastest growing type of electricity generation-quadrupling (翻两番)worldwide between 1999 and 2005. Modem wind farms consist of turbines that generate electricity. Though it will be more expensive, there is more than enough wind to provide the world’s entire energy needs. Wind farms come in onshore and offshore forms. They can often end up at spots of natural beauty, and are often unpopular with residents. And turbines are not totally harmless, they can interfere with radar, alter climate and kill sea birds. Scotland is building Europe’s largest wind farm, which will power 200, 000 homes. The UK’s goal is to generate one-fifth of power from renewable sources, mainly wind, by 2020. But this may cause problems, because wind is unreliable. One of the problems with wind farms is that（）.
第二篇Good Table MannersManners play an important part in making a favorable impression at the dinner table. Here are some general rules:Napkin (餐巾) useThe meal begins when the host unfolds his or her napkin. This is your signal to do the same, so place your napkin on your lap. Unfold it completely if it is a small napkin, or in half, lengthwise (纵向地), if it is a large dinner napkin.If you need to leave the table during the meal, place your napkin on your chair as a signal to your server that you will be returning. Once the meal is over, place your napkin neatly on the table to the right of your dinner plate. Do not refold it.Use a napkin only for your mouth. Never use it for your nose, face or forehead.Use of utensils (餐具)Start with the knife, fork or spoon furthest from your plate, and work your way in, using one utensil for each course.If soup is served, remember to spoon away from yourself. This helps stop the drips. Do not put the entire soup spoon in your mouth. Instead, fill a soup spoon about 75 per cent with soup, and sip (啜饮) it from the side noiselessly.After finishing dinner, place the knife and fork parallel to one another across the Plate with the knife alade facing inward toward the plate.Using your f’ingersHere’s a list of finger foods: sandwiches, cookies, small fruits or berries with stems, French fries and potato chips, hamburgers.Chew(咀嚼) with your mouth closed and don’t make noise; don’t talk with your mouth full.Bread must be broken with your hands. It is never cut with a knife.Don’t pick something out of your teeth. Instead, excuse yourself to the bathroom.If possible, try not to cough at the table.Do not put your elbows(肘) on the table. In France, it is essential to have both hands above the table at the same time.Do not put bones or anything else on the table. Things that are not eaten should be put on your plate. The napkin is used only for（）.
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