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Nuclear power"s danger to health, safety, and even life itself can be summed up in one word: radiation. Nuclear radiation has a certain mystery about it, partly because it cannot be detected by human senses. It can"t be seen or heard, or touched or tasted, even though it may be all around us. There are other things like that. For example, radio waves are all around us but we can"t sense radioactivity without a radiation detector. But unlike common radio waves, nuclear radiation is not harmless to human beings and other living things.At very high levels, radiation can kill an animal or human being outright by killing masses of cell in vital organs. But even the lowest levels can do serious damage. There is no level of radiation that is completely safe. If the radiation does not hit anything important, the damage may not besignificant.This is the case when only a few cells are hit, and if they are killed outright. Your body will replace the dead cells with healthy ones. But if the few cells arc only damaged, and if they reproduce themselves, you may be in trouble. They reproduce themselves in a deformed way. They can grow into cancer. Sometimes this does not show up for many years.This is another reason for some of the mystery about nuclear radiation. Serious damage can be done without the victim being aware at the time that damage has occurred. A person can be irradiated and feel fine, then die of cancer five, ten, or twenty years later as a result. Or a child can be born weak or liable to serious illness as a result of radiation absorbed by its grandparents. It is not too careful to prevent from the radiation. Radiation can hurt us. We must know the truth. The word "significant" in paragraph 2 most probably means ______.
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Nuclear power"s danger to health, safety, and even life itself can be summed up in one word: radiation. Nuclear radiation has a certain mystery about it, partly because it cannot be detected by human senses. It can"t be seen or heard, or touched or tasted, even though it may be all around us. There are other things like that. For example, radio waves are all around us but we can"t sense radioactivity without a radiation detector. But unlike common radio waves, nuclear radiation is not harmless to human beings and other living things.At very high levels, radiation can kill an animal or human being outright by killing masses of cell in vital organs. But even the lowest levels can do serious damage. There is no level of radiation that is completely safe. If the radiation does not hit anything important, the damage may not besignificant.This is the case when only a few cells are hit, and if they are killed outright. Your body will replace the dead cells with healthy ones. But if the few cells arc only damaged, and if they reproduce themselves, you may be in trouble. They reproduce themselves in a deformed way. They can grow into cancer. Sometimes this does not show up for many years.This is another reason for some of the mystery about nuclear radiation. Serious damage can be done without the victim being aware at the time that damage has occurred. A person can be irradiated and feel fine, then die of cancer five, ten, or twenty years later as a result. Or a child can be born weak or liable to serious illness as a result of radiation absorbed by its grandparents. It is not too careful to prevent from the radiation. Radiation can hurt us. We must know the truth. Radiation can cause serious consequences even at the lowest level ______.
In the United States, the first day nursery, was opened in 1854. Nurseries were established in various areas during the 1 half of the 19th century; most of 2 were charitable. Both in Europe and in the U.S., the day nursery movement received great 3 during the First World War, when 4 of manpower caused the industrial employment of unprecedented (前所未有) numbers of women. In some European countries nurseries were established 5 in munitions (军火) plants, under direct government sponsorship. 6 the number of nurseries in the U.S. also rose 7 , this rise was accomplished without government aid of any kind. During the years following the First World War, 8 , federal, State, and local governments gradually began to exercise a measure of control 9 the day nurseries, chiefly by 10 them.The 11 of the Second World War was quickly followed by an increase in the number of day nurseries in almost all countries, as women were 12 called up on to replace men in the factories. On this 13 the U.S. government immediately came to the support of the nursery schools, 14 $6,000,000 in July, 1942, for a nursery school program for the children of working mothers. Many States and local communities 15 this Federal aid. By the end of the war, in August, 1945, more than 100, 000 children were being cared 16 in daycare centers receiving Federal 17 . Soon afterward, the Federal government 18 cut down its expenditures for this purpose and later 19 them, causing a sharp drop in the number of nursery schools in operation. However, the expectation that most employed mothers would leave their 20 at the end of the war was only partly fulfilled.
In the United States, the first day nursery, was opened in 1854. Nurseries were established in various areas during the 1 half of the 19th century; most of 2 were charitable. Both in Europe and in the U.S., the day nursery movement received great 3 during the First World War, when 4 of manpower caused the industrial employment of unprecedented (前所未有) numbers of women. In some European countries nurseries were established 5 in munitions (军火) plants, under direct government sponsorship. 6 the number of nurseries in the U.S. also rose 7 , this rise was accomplished without government aid of any kind. During the years following the First World War, 8 , federal, State, and local governments gradually began to exercise a measure of control 9 the day nurseries, chiefly by 10 them.The 11 of the Second World War was quickly followed by an increase in the number of day nurseries in almost all countries, as women were 12 called up on to replace men in the factories. On this 13 the U.S. government immediately came to the support of the nursery schools, 14 $6,000,000 in July, 1942, for a nursery school program for the children of working mothers. Many States and local communities 15 this Federal aid. By the end of the war, in August, 1945, more than 100, 000 children were being cared 16 in daycare centers receiving Federal 17 . Soon afterward, the Federal government 18 cut down its expenditures for this purpose and later 19 them, causing a sharp drop in the number of nursery schools in operation. However, the expectation that most employed mothers would leave their 20 at the end of the war was only partly fulfilled.
What might driving on an automated highway be like The answer depends on what kind of system is ultimately adopted. Two distinct types are on the drawing board. The first is a special purpose lane system, in which certain lanes are reserved for automated vehicles. The second is a mixed traffic system: fully automated vehicles would share the road with partially automated or manual driven cars. A special purpose lane system would require more extensive physical modifications to existing highways, but it promises the greatest gains in freeway (高速公路) capacity.Under either scheme, the driver would specify the desired destination, furnishing this information to a computer in the car at the beginning of the trip or perhaps just before reaching the automated highway. If a mixed traffic system way was in place, automated driving could begin whenever the driver was on suitably equipped roads. If special purpose lanes were available, the car could enter them and join existing traffic in two different ways. One method would use a special onramp (入口引道). As the driver approached the point of entry for the highway, devices installed on the roadside would electronically check the vehicle to determine its destination and to ascertain that it had the proper automation equipment in good working order. Assuming it passed such tests, the driver would then be guided through a gate and toward an automated lane. In this case, the transition from manual to automated control would take place on the entrance ramp. An alternative technique could employ conventional lanes, which would be shared by automated and regular vehicles. The driver would steer onto the highway and move in normal fashion to a "transition" lane. The vehicle would then shift under computer control onto a lane reserved for automated traffic. (The limitation of these lanes to automated traffic would, presumably, be well respected, because all trespassers (非法进入者) could be swiftly identified by authorities. )Either approach to joining a lane of automated traffic would harmonize the movement of newly entering vehicles with those already traveling. Automatic control here should allow for smooth merging without the usual uncertainties and potential for accidents. And once a vehicle had settled into automated travel, the driver would be free to release the wheel, open the morning paper or just relax. Which of the following is true about driving on an automated highway
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