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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 nearest black holes are hundreds of light years away from us.（）
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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. According to the passage, resources like wind are（）.
A. that person’s health B. a scientific answer C. scientific researchers D. the genes E. the function F. the size Genetic mutations in a person’s genome may affect______.
在填制入境货物报检单时，进口货物的品名应与进口合同一致，但废旧货物应在品名中特别注明。（）
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. 51（）
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