单选题请根据短文内容为每处空白确定1个最佳选项 　　　　　　　　　　　　　　　　　　　　　　　　{{B}}Taking a Nap During the Day{{/B}} Medical experts say most Americans do not get enough sleep. They say more Americans need to {{U}} (51) {{/U}} for a short period in the middle of the day. They are advising people to sleep lightly {{U}} (52) {{/U}}continuing with other activities. One study earlier this year found that persons who sleep for a few minutes during the day were less likely to die of {{U}}(53) {{/U}} disease. The study followed more than 2,300 Greek adults {{U}}(54) {{/U}} about six years. Adults who rested for half an hour at least three times a week had a 37 percent lower {{U}} (55) {{/U}}of dying from heart disease than those who did not nap. Study organizers said the strongest {{U}}(56) {{/U}}was in working men. They said naps might improve health by mitigating (减低) tension {{U}}(57) {{/U}} by work. Some European and Latin American businesses have Supported the idea of {{U}}(58) {{/U}}for many gears. They urge(催促)people to {{U}}(59) {{/U}}work,go home and have a nap before returning. In the United States, some companies let workers rest briefly in their offices. They believe this reduces mistakes and accidents,and also {{U}}(60) {{/U}}the amount of work a person can do. Sleep experts say it is likely that people {{U}}(61) {{/U}}more mistakes at work than at other times. They say people should not carry out important duties {{U}}(62) {{/U}} they feel sleepy. And they say the ]rest thing to do is to take a nap. About twenty minutes of rest is all you {{U}}(63) {{/U}}. Experts say this provides extra energy and can increase your {{U}}(64) {{/U}} until the end of the day. But experts {{U}} (65) {{/U}} that a nap should last no more than twenty to thirty minutes. A longer nap will put the body into deep sleep and waking up will be difficult.

单选题According to the passage,resources like wind are

单选题They're petitioning for better facilities for the disabled on public transport.

单选题Her Upeers/U were her worst critics.

单选题According to the passage, we can avoid a worldwide water shortage in the future, by

单选题If you made a list of all the jobs performed by the different kinds of energy, you would fill many pages. Nuclear energy is used in some areas of the United States. But there are dangers. Waste materials from nuclear (51) would destroy life if they leaked (52) the land. When nuclear energy is produced, a lot of (53) is produced, too, so a flow of lake or ocean water is used to cool the operations. Then the water (54) to its source. If the returning water were too hot, it would destroy fish and other (55) . Cow manure is being used to produce a kind of (56) . The manure from farms is put into a machine to convert it to a liquid. Then the gas is formed (57) a natural process. If the converter were not so (58) at the present time, it would be used in many places to provide (59) . Garbage has become an energy source. It (60) to oil, steam, or electricity, or it is used on the land. But recent (61) about power supplies has led to increased interest in the use of wind (62) a source of electrical power. Windmills are clean and they (63) no waste. And they use a (64) resource. Some scientists consider that wind energy systems can fulfill a valuable (65) in meeting the energy needs of industrialized nations and of the developing world.

单选题One of the concerns the CDC has is that

单选题Avalanche (雪崩) and Its Safety An avalanche is a sudden and rapid flow of snow, often mixed with air and water, down a mountainside. Avalanches are (51) the biggest dangers in the mountains for both life and property. All avalanches are caused by an overburden of material, typically snowpack (积雪场), that is too massive and unstable for the slope (52) supports it. Determining the critical load, the amount of over-burden which is (53) to cause an avalanche, (54) a complex task involving the evaluation of a number of factors. Terrain slopes flatter than 25 degrees or steeper than 60 degrees typically have a low (55) of avalanche. Snow does not (56) significantly on steep slopes; also, snow does not (57) easily on fiat slopes. Human-triggered (激发) avalanches have the greatest incidence (发生率) when the snow's angle of rest is (58) 35 and 45 degrees; the critical angle, the angle at which the human incidence of avalanches is greatest, is 38 degrees. The rule of thumb (经验法则) is: A slope that is (59) enough to hold snow but steep enough to ski has the potential to generate an avalanche, regardless of the angle. Additionally, avalanche risk increases with (60) ; that is, the more a slope is disturbed by skiers, the more likely it is that an avalanche will occur. Due to the complexity of the subject, winter travelling in the backcountry (人烟稀少的地区) is never 100% safe. Good avalanche safety is a continuous (61) , including route selection and examination to the snowpack, weather (62) , and human factors. Several well-known good habits can also (63) the risk. If local authorities issue avalanche risk reports, they should be considered and all warnings should be paid (64) to. Never follow in the tracks of others without your own evaluations; snow conditions are almost certain to have changed since they were made. Observe the terrain and note obvious avalanche paths where plants are (65) or damaged. Avoid traveling below others who might trigger an avalanche.

单选题Her life is becoming more diverse .

单选题I won"t tolerate that kind of behavior.

单选题In 1816 it seemed inevitable that Southern states would break away from the Union.

单选题The room is small but cozy. A. cold B. splendid C. comfortable D. gorgeous

单选题Even in a highly modernized country, Umanual/U work is still needed:

单选题 The Development of Personality Personality is to large extent inherent. A-type parents usually bring A-type offspring. But the environment must also have a profound effect, since if competition is important to the parents, it is likely to become a major factor in the lives of their children. One place where children soak up (浸泡) a characteristic is school, which is, by its very nature, a highly competitive institution. Too many schools adopt the "win at all costs" moral standard and measure their success by sporting achievements. The current passion for making children compete against their classmates or against the clock produces a two-layer system, in which competitive A-types seem in some way better than their B-type fellows. Being too keen to win can have dangerous consequences: Remember that Philippines, the first marathon runner, dropped dead seconds after saying, "Rejoice, We conquer!" By far the worst form of competition in schools is the disproportionate emphasis on examinations. It is a rare school that allows pupils to concentrate on those things they do well. The merits of competition by examination are somewhat questionable, but competition in the certain knowledge of failure is positively harmful. Obviously, it is neither practical nor desirable that all A youngsters change into B's. The world needs types, and schools have an important duty to try to fit a child's personality to hide possible future employment. It is top management. If the preoccupation of schools with academic work was lessened, more time might be spent teaching children surer values. Perhaps selection for the caring professions, especially medicine, could be made less by good grades in chemistry and more by such considerations as sensitivity and sympathy. It is surely a mistake to choose our doctors exclusively form A-type stock. B's are important and should be encouraged.

单选题The fighter plane {{U}}fell{{/U}} into a mountain after take-off, its bombs exploding as it hit the ground.

单选题Thick clouds Uobscured/U the stars from view.

单选题 下面的短文后列出了7个句子，请根据短文的内容对每个句子做出判断：如果该句提的是正确信息，请选择A；如果该句提是错误信息，请选择B；如果该句的信息文中没有提及，请选择C。 Artificial Speech Because speech is the most convenient form of communication, in the future we want essentially natural conversations with computers. The primary point of contact will be a simple device that will act as our window into the world. It will have to be small enough to slip into pour pocket, so there will be a screen but no keyboard: you will simply talk to it. The device will be permanently connected to the Internet and will beep relevant information up to you as it comes in. Such devices will evolve naturally in the next five to ten years. Just how quickly people will adapt to a voice-based Internet world is uncertain. Many believe that, initially at least, we will need similar conventions for the voice to those we use at present on screen : click, back, forward, and so on. But soon you will undoubtedly be able to interact by voice with all those IT-based services you currently connect with over the Internet by means of a keyboard. This will help the Internet serve the entire population. Changes like this will encompass (围绕、包围) the whole world. Because English is the language of science, it will probably remain the language in which the technology is most advanced, but most speech, recognition techniques are transferable to other languages provided (假如、若是) there is sufficient motivation to undertake the work. Of course, in any language there are still huge problems for LIS to solve. Carefully dictated, dear speech can now be understood by computers with only a 4～5 percent error rate, but even the most advanced technology still records 30～40 percent errors with spontaneous' speech. Within ten years we will have computers that respond to goal-directed conversation, but for a computer to have a conversation that takes into account human social behaviors is probably 50 years off. We are not going to be chatting to the big screen in the living room just yet. In the past insufficient speed and memory have held LIS back, but these days they are less of an issue. However, there are those in the IT community who believe that current techniques will eventually hit a brick wall. Personally, I believe that incremental (不断增长的)developments in performance are more likely. But it is true that by about 2040 or so, computer architectures will need to become highly parallel(并行的) if performance is to keep increasing. Perhaps that will inspire some radically new approaches to speech understanding that will replace the methods we are developing now.

单选题Snow Ranger The two things, snow and mountains, which are needed for a ski area are the two things that cause avalanches, large mass of snow and ice crushing down the side of a mountain, often called "White Death." It was the threat of the avalanche and its record as a killer of man in the western mountains that created the snow ranger. He first started on avalanche control work in the winter of 1937, 38 at Alta, Utah, in Wasatch National Forest. This mountain valley was becoming well known to skiers. It was dangerous. In fact, more than 120 persons had lost their lives in 1936 and another 200 died in 1937 as a result of avalanches before it became a major ski area. Thus, development of Alta and other major ski resorts in the west was dependent upon controlling the avalanche. The Forest Service set out to do it, and did with its corps of snow rangers. It takes many things to make a snow ranger. The snow ranger must be in excellent physical condition. He must be a good skier and a skilled mountain climber. He should have at least a high school education, and the more college courses in geology, physics, and related fields he has, the better. He studies snow, terrain, wind, and weather. He learns the conditions that produce avalanches. He learns to forecast avalanches and to bring them roaring on down the mountainsides to reduce their killing strength. The snow ranger learns to do this by using artillery, by blasting with TNT, and by the difficult and skillful art of skiing avalanches down. The snow ranger, dressed in a green parka which has a bright yellow shoulder patch, means safety for people on ski slopes. He pulls the trigger on a 75 mm. Recoilless rifle, skis waist deep in powder testing snow stability, or talks with the ski area's operator as he goes about his work to protect the public from the hazards of deep snow on steep mountain slopes.

单选题The megaphone makes the voice sound louder because it points sound waves in one direction and keeps them from {{U}}spreading out{{/U}} in all directions.

单选题There are {{U}}various{{/U}} kinds of food in China.