单选题In order to limit the damage and to prevent some of the suffering resulting from earthquakes, scientists are working on ways to enable accurate prediction, Special instruments are used to help people record, for example, shaking of the earth. Scientist are trying to find methods that will enable them to indicate the exact time, location and size of an earthquake. Certain phenomena have been observed which are believed to be the signs of imminent(即将发生的) earthquakes. These include strange behaviours of some animals, the changes in the content of mineral water, etc. The magnetic properties of rocks may also display special pattern before major earthquakes happen. Signs of imminent earthquakes include all the following BUTA. strange behaviours of animals.B. changes in the content of mineral water.C. the magnetic properties of rocks.D. dramatic change in climat

单选题Housewives who do not go out to work often feel they are not working to their full ability .

单选题What is said about cell phone use in the mid-1980s in paragraph 5?

单选题These figures do not take into account the changes that have taken place in recent years. A. consider B. call C. catch D. cancel

单选题We tried to restrict our conversation to arguments relevant to the topic.

单选题Calculating Crime When you think about math, you probably don't think about breaking the law, solving mysteries or finding criminals. But a mathematician in Maryland does, and he has come up with mathematical tools to help police find criminals. People who solve crimes look for patterns that might reveal the identity of the criminal. It's long been believed, for example, that criminals will break the law closer to where they live. simply because it's easier to get around in one's own neighborhood. If police see a pattern of robberies in a certain area, they may look for a suspect who lives near the crime scenes. So, the farther away from the area a crime takes place, the less likely it is that the same criminal did it. But Mike O'Leary, a mathematician at Towson University in Maryland, says that this kind of approach may be too simple. He says that police may get better clues to the location of an offender's home base by combining these patterns with a city's layout and historical crime records. The records of past crimes contain geographical information and can reveal easy targets--that is, the kind of stores that might be less difficult to rob. Because these stores are along roads, the locations of past crimes contain information about where major streets and intersections(十字路口) are. O'Leary is writing a new computer program that will quickly provide this kind of information for a given city. His program also includes information about the people who live in the city, and information about how a criminal's patterns change with age. (It's been shown, for example, that the younger the criminal, the closer to home the crime. ) Other computer programmers have worked on similar software, but O'Leary's uses more math. The mathematician plans to make his computer program available, free of charge, to police departments around the country. The program is just one way to use math to fight crime. O'Leary says that criminology--the study of crime and criminals contains a lot of good math problems. "I feel like I'm in a gold mine and I'm the only one. who knows what gold looks like." he says. "It's a lot of fun. /

单选题 阅读下面这篇短文，短文后列出7个句子，请根据短文的内容对每个句子做出判断。 {{B}}Changes in Museums{{/B}} Museums have changed. They are no longer places that one "should" visit, they are places to enjoy and learn. At a science museum in Ontario, Canada, you can feel your hair stand on end as harmless electricity passes through your body. At the Metropolitan (成都市的) Museum of Art in New York City, you can look at the seventeenth century instruments while listening to their music. At New York's American Museum of Natural History recently, you can help make a bone-by-bone reproduction of the museum's dinosaur(恐龙), a beast that lived 200 million years age. More and more museum directors are realizing that people learn best when they can somehow become part of what they are seeing. In many science museums, for example, there are no guided tours. The visitor is encouraged to touch, listen, operate, and experiment so as to discover scientific principles for himself. The purpose is not only to provide fun but also to help people feel at home in the world of science. The theory is that people who do not understand science will probably fear it, and those who fear science will not use it to best advantage. One cause of all these changes is the increase in wealth and leisure time. Another cause is the rising percentage of young people in the population. Many of these young people are college students or college graduates, Leon F. Twiggs, a young black professor of art once said, "They see things in a new and different way. They are not satisfied to stand and look at works of art; they want art they can participate(参加) in. "The same is true of science and history.

单选题Avalanche 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 over-burden of material, typically snowpack, 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 no (57) easily on fiat slopes. Human-triggered avalanches have the greatest incidence 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 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 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She is incapable of doing the demanding job.

单选题US citizens and businesses have long complained that many of the government's rules are written in overly technical, complicated language. The Occupational Safety and Health Administration (OSHA) has particularly been the subject of much criticism and debate. This agency makes and enforces rules to ensure employee health and safety on the job. The problem is, even after reading the roles several times, employees often don't know what is expected of them. OSHA has been the subject of much criticism mainly becauseA. its rules are wrongly expressed.B. its rules focus on too many details.C. its rules use many technical words.D. its rules are beyond comprehension.

单选题Gas does Uaccumulate/U in the mines around here.

单选题However bad the situation is, the majority is {{U}}unwilling{{/U}} to risk change.

单选题 Kite Kite flying is the sport of sending up into the air, by means of the wind, a light frame covered with paper, plastic or doth. The frame can be one of many different shapes and is attached to a long string held in the hand or wound on a drum. Kites have a long history practical application and many different types of kite have been developed to serve various purposes. The ancient Chinese used bird-kites to carry ropes across rivers and valleys. The current folding kite which will dive excitingly is an improved type of such a kite. With its long flat body and single pair of bird like wings, it looks just like a large bird in the air. The modern version is usually made of tissue paper rather than the traditional silk. Man-lifting kites were developed in ancient times, again by the Chinese, for getting information from walled cities and army camps. In fact, as recently as World War Ⅱ, German U-boats flew kites from their towers to lift people into the air to watch the land. These kites, which are no longer in existence, were made of lightweight cloth. They were much larger and stronger than the Chinese ones. Their design, however, was simply that of the cutter kite. Smaller in size, this type of kite is still very popular as a toy for children, being easy to make with a diamond-shaped frame, no wings and brown-paper covering. Box kites are another type of kite found in toy shops today. The first box kite, named for its box-like body, was developed in the 19th century to test theories of flight and this type of cotton-covered kite greatly assisted the success of early airplanes. These kites are the ancestors of a heavier version of the box kite, called the double box kite, which consists of two main sections, placed side by side. Developed for the peacetime purpose of fishing in strong sea wind, it is the only modern kite described which has practical value. A long-lasting plastic material has to be used for this kite, which carries fishing lines.

单选题The attitude of the author towards the research project is

单选题 Transportation use a to Be Much Slower than It Is Now For many years in tile desert, camels used to be the only form of transportation. Before the (51) of modern trains, camel trains used to carry al! the goods for trading between Central Africa and Europe. Traders sometimes (52) to put together camel trains with 10,000 to 15,000 animals. Each animal often carried (53) 400 pounds and it could travel twenty miles a day. This form of transportation was so important (54) camels were called the "ship of the desert". Now modern trains travel across the desert in a very (55) time. One engine can pull as much weight as 135,000 (56) ,in addition, trains use special cars for their load. Refrigerator cars carry food; boxcars carry heavy goods; stock cars carry animals; and tank cars carry oil. (57) travel has changed, too. The earliest planes were biplanes, with two sets of wings. The top speed of this plane was 60 miles per hour. The pilots used to sit or lie on the wings in the open air. The plane (58) sometimes stopped in the middle of a trip. It used to be (59) to fly in bad weather. In snow or in rain, the wings frequently became icy. (60) the plane might go down. Mechanical improvements during the First World War changed airplanes. Monoplanes took the place of biplanes. Pilots flew inside of covered cabins. Still, even these planes were small and expensive. Only (61) people were able to travel in airplanes. Now modern jets make air travel possible for all people. (62) place in the world is more than 1 hours away by jet. Further improvements have (63) the cost of flying, and they have made air travel much safer than it used to be. A modern 707 can carry 170 people and can fly at 600 miles per hour. People (64) used to eat, sleep, or watch movies on airplanes. (65) these things are a normal part of air travel!

单选题Please Fasten Your Seatbelts Severe turbulence (湍流) can kill aircraft passengers. Now, in test flights over the Rocky Mountains, NASA (美国航空航天局) engineers have successfully detected clear-air turbulence up to 10 seconds before an aircraft hits it. Clear-air turbulence often catches pilots by surprise. Invisible to radar, it is difficult to forecast it and can hurl (用力抛出去) passengers out of the cabin. In December 1997, one passenger died and a hundred others were injured when unexpected rough air caused a United Airlines flight over the Pacific to drop 300 meters in a few seconds. However, passengers can avoid serious injury by fastening their seatbelts. "It is the only antidote (对策) for this sort of thing," says Rod Bogue, project manager at NASA"s Dryden Flight Research Center in Edwards, California. The centre"s new turbulence detector is based on lidar, laser, or radar. Laser pulses are sent ahead of the plane and these are then reflected back by particles in the air. The technique depends on the Doppler Effect. The wavelength of the light shifts according to the speed at which the particles are approaching. In calm air, the speed equals the plane"s airspeed. But as the particles swirl (打旋) in rough air, their speed of approach increases or decreases rapidly. The rate of change in speed corresponds to the severity (激烈程度) of the turbulence. In a series of tests that began last month, a research jet flew repeatedly into disturbed air over the mountain ridges (山脉) near Pueblo, Colorado. The lidar detector spotted turbulence between 3 and 8 kilometers ahead, and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountered. Bogue says that he had "a comfortable amount of time" to fasten his seatbelt. The researchers are planning to improve the lidar"s range with a more powerful beam. The system could be installed on commercial aircraft in the next few years.

单选题The most pressing problem that any country faces is how to use its scarce natural resources.A. puzzlingB. difficultC. terrifyingD. urgent

单选题The construction of the bridge goes on very well.A. instructionB. destructionC. conductionD. building

单选题Prohibition in the United States {{U}}ushered in{{/U}} an era of crime and corruption.