单选题Companies whose profits do not exceed $ 1500 in any one year may opt to pay income tax at the rate of 20%.A. chooseB. operateC. manageD. decide

单选题In the first decades of this century, the individual gene could be worked with fruitfully.A. blindlyB. completelyC. productivelyD. carefully

单选题 First Self Contained Heart Implanted A patient on the brink of death has received the world's first self-contained artificial heart—a battery powered device about the size of a softball that runs without the need for wires, tubes or hoses sticking out of the chest. Two surgeons from the University of Louisville implanted the titanium and plastic pump during a seven-hour operation at Jewish Hospital Monday. The hospital said the patient was "awake and responsive" Tuesday and resting comfortably. It refused to release personal details. The patient had been expected to die within a month without the operation, and doctors said they expected the artificial heart to extend the person's life by only a month. But the device is considered a major step toward improving the patient's quality of life. The new pump, called AbioCor, is also a technological leap from the mechanical hearts used in the 1980s, which were attached by wires and tubes to bulky machinery outside the body. The most famous of those, the Jarvic-7, used air as a pumping device and was attached to an apparatus about the size of a washing machine. "I think it's potentially a major step forward in the artificial heart development," said Dr. David Faxon, president of the American Heart Association. However, he said the dream of an implantable, permanent artificial heart is not yet a reality. "This is obviously an experimental device whose long-term success has to be demonstrated." Only about half of the 4,200 Americans on a waiting list for donor hearts received them last year, and most of the rest died. Some doctors, including Robert Higgins, chairman of cardiology at the Medical College of Virginia in Richmond, said artificial hearts are unlikely to replace donor hearts. "A donor heart in a good transplant can last 15 to 30 years," he said. "It's going to be hard to replace that with a machine." The AbilCor has a 2-pound pumping unit, and electronic controls that adjust the pumping speed based on the body's needs. It is powered by a small battery pack worn outside the body that transmits current through the skin.

单选题New Foods and the New World In the last 500 years, nothing about people-not their clothes, ideas, or languages-has changed as much as what they eat. The original chocolate drink was made from the seeds of the cocoa tree by South American Indians. The Spanish introduced it to the rest of the world during the 1500's. And although it was very expensive, it quickly became fashionable. In London shops where chocolate drinks were served became important meeting places. Some still exist today. The potato is also from the New World. Around 1600, the Spanish brought it from Peru to Europe, where it soon was widely grown. Ireland became so dependent on it that thousands of Irish people starved when the crop failed during the "Potato Famine" of 1845-1846, and thousands more were forced to emigrate to America. There are many other foods that have traveled from south America to the Old World. But some others went in the opposite direction. Brazil is now the world's largest grower of coffee, and coffee is an important crop in Colombia and other South American countries. But it is native to Ethiopia. It was first made into a drink by Arabs during the 1400's. According to an Arabic legend, coffee was discovered when a goatherd named Kaldi noticed that his goats were attracted to the red berries on a coffee bush. He tried one and experienced the "wide-awake" feeling that one-third of the world's population now starts the day with.

单选题{{B}}第三篇{{/B}} Why does cream go bad faster than butter? Some researchers think they have the answer, and it comes down to the structure of the food, not its chemical composition--a finding that could help rid some processed foods of chemical preservatives. Cream and butter contain pretty much the same substances, so why cream should sour much faster has been a mystery. Both are emulsions--tiny globules(小球体)of one liquid evenly distributed throughout another. The difference lies in what's in the globules and what's in the surrounding liquid, says Brocklehurst, who led the investigation. In cream, fatty globules drift about in a sea of water. In butter, globules of a watery solution are locked away in a sea of fat. The bacteria which make the food go bad prefer to live in the watery regions of the mixture. "This means that in cream, the bacteria are free to grow throughout the mixture," he says. When the situation is reversed, the bacteria are locked away in compartments(隔仓室)buried deep in the sea of fat. Trapped in this way, individual colonies cannot spread and rapidly run out nutrients(养料). They also slowly poison themselves with their waste products. "In butter, you get a self--limiting system which stops the bacteria growing," says Broeklehurst. The researchers are already working with food companies keen to see if their products can be made resistant to bacterial attack through alterations to the food's structure. Brocklehurst believes it will be possible to make the emulsions used in salad cream, for instance, more like that in butter. The key will be to do this while keeping the salad cream liquid and not turning in into a solid lump.

单选题In the United States,the national flag is usually displayed outdoor between sunrise and sunset.

单选题Patricia stared at the other girls with resentment .

单选题I didn't ask because I was afraid of looking Ustupid/U.

单选题Below 600 feet ocean waters range from dimly lit to completely dark. A. inadequately B. hardly C. faintly D. sufficiently

单选题He has {{U}}luxurious{{/U}} habits of throwing money about like dirt.

单选题I am feeling {{U}}a lot{{/U}} more healthy than I was. A. many B. no C. much D. some

单选题About twenty years ago, all important resources in our country were Uallocated/U by the central government.

单选题The book made a great impact on its readers.

单选题These factors interact intimately and cannot be separated.

单选题InBritain and many other countries appraisal is now a tool of management.

单选题Explorer of the Extreme Deep Oceans cover more than two-thirds of our planet. Yet, just a small fraction of the underwater world has been explored. Now, scientists at the Woods Hotel Oceanographic Institution (WHOI) in Massachusetts are building an underwater vehicle that will carry explorers as deep as 6,500 meters (21,320 feet). The new machine, known as a manned submersible or human-operated vehicle (HOV), will replace another one named Alvin which has an amazing record of discovery, playing a key role in various important and famous undersea expeditions. Alvin has been operating for 40 years but can go down only 4,500 meters (14,784 feet). It"s about time for an upgrade, WHOI researchers say. Alvin was launched in 1964. Since then, Alvin has worked between 200 and 250 days a year, says Daniel Fornari, a marine geologist and director of the Deep Ocean Exploration Institute at WHOI. During its lifetime, Alvin has carried some 12,000 people on a total of more than 3,000 dives. A newer, better versions of Alvin is bound to reveal even more surprises about a world that is still full of mysteries, Fornari says. It might also make the job of exploration a little easier. "We take so much for granted on land," Fornari says. "We can walk around and see with our eyes how big things are. We can see colors, special arrangements." Size-wise, the new HOV will be similar to Alvin. It"ll be about 37 feet long. The setting area inside will be a small sphere, about 8 feet wide, like Alvin, it"ll carry a pilot and two passengers. It will be just as maneuverable. In most other ways, it will give passengers more opportunities to enjoy the view, for one thing. Alvin has only three windows, the new vehicle will have five, with more overlaps so that the passengers and the pilot can see the same thing. Alvin can go up and down at a rate of 30 meters every second, and its maximum speed is 2 knots (about 2.3 miles per hour), while the new vehicle will be able to ascend and descend at 44 meters per second. It"ll reach speeds of 3 knots, or 3.5 miles per hour.

单选题Domestic demand may {{U}}thus{{/U}} decelerate to a more sustainable growth rate, and the unemployment rate may rise slightly.

单选题 Play Play is the principal business of childhood, and in recent years research has shown the great importance of play in the development of a human being. From earliest infancy, every child needs opportunity and the right materials for play, and the main tools of play are toys. Their main function is to suggest, encourage and assist play. To succeed in this they must be good toys, which children will play with often, and will come back to again and again. Therefore it is important to choose suitable toys for different stages of a child's development. In recent years research on infant development has shown that the standard a child is likely to reach, within the range of his inherited abilities, is largely determined in the first three years of his life. So a baby's ability to profit from the right play materials should not be underestimated. A baby who is encouraged and stimulated, talked to and shown things and played with, has the best chance of growing up successfully. In the next stage, from three to five years old, curiosity knows no bounds. Every type of suitable toy should be made available to the child, for trying out, experimenting and learning, for discovering his own particular ability. Bricks and jigsaws (七巧板) and construction toys; painting, scribbling (涂鸦) and making things; sand and water play; toys for imaginative and pretending play; the first social games for learning to play and get on with others. But the third stage of play development—from five to seven or eight years—the child is at school. But for a few more years play is still the best way of learning, at home or at school. It is easier to see which type of toys the chills most enjoys. Until the age of seven or eight, play and work mean much the same to a child. But once reading has been mastered, then books and school become the main source of learning. Toys are still interesting and valuable, they lead on to new hobbies, but their significance has changed—to a child of nice or ten years, toys and games mean, as to adults, relaxation and 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}} Nurses{{/B}} The physicians in a hospital form the core of the medical staff. But they could not provide effective medical care to their patients without the help of numerous other medical workers. From the angle of the patients, the nursing staff is particularly important. Nurses are usually in close contact with patients as long as they are in the hospital. A nurse does not study for as many years as a doctor. However, each must be equally trained. Caring for sick persons requires a great deal of patience and concern. Most nurses work long days, and they often must work at odd hours or during the night. The nursing staff in a hospital is usually quite large and various. Nursing services, after all, must be provided on a 24-hour basis. There are professional(专业的) nurses, practical nurses ,nurse's aids, and orderlies(勤杂工). The general term nurse refers to a person trained to offer bedside care to sick persons. Under the supervision(管理) of the head nurse, the nursing staff in a hospital ward must attend to patients' needs. This responsibility continues around the clock, and so nurses must work in shifts. A shift is a period of duty, usually eight hours in length. The nurses on the ward rotate(轮换) their shifts. Some take turns working night duty; other work odd shifts. All of them work out of a central area on the ward called the nurse's station. A nurse must always be on her guard. She can never afford to be careless. This is true in all nursing situations, but it is especially true in the intensive care unit. Patients under intensive care are critically ill, and they must be monitored at all times. The nurses who do intensive care duty have one of the most demanding jobs in the hospital.

单选题With immense relief I stopped running.