单选题 下面有3篇短文，每篇短文后有5道题，每道题后面有4个选项。{{B}}第一篇{{/B}} {{B}}The Gene Industry{{/B}} Major companies are already in pursuit of commercial applications of the new biology. They dream of placing enzymes in the automobile to monitor exhaust and send data on pollution to a microprocessor that will then adjust the engine. They speak of what the New York Times calls "metal-hungry microbes that might be used to mine valuable trace metals from ocean water". They have already demanded and won the right to patent new lifeforms. Nervous critics, including many scientists, worry that there is corporate, national, international, and inter-scientific rivalry in the entire biotechnological field. They create images not of oil spills, but of "microbe spills" that could spread disease and destroy entire populations. The creation and accidental release of extremely poisonous microbes, however, is only one cause for alarm. Completely rational and respectable scientists are talking about possibilities that stagger the imagination. Should we breed people with cow-like stomachs so they can digest grass and hay, thereby relieving the food problem by modifying us to eat lower down on the food chain? Should we biologically alter workers to fit the job requirement, for example, creating pilots with faster reaction times or assembly-line workers designed to do our monotonous work for us? Should we attempt to eliminate "inferior" people and breed a "super-race"? (Hitler tried this, but without the genetic weaponry that may soon issue from our laboratories.) Should we produce soldiers to do our fighting? Should we use genetic forecasting to pre-eliminate "unfit" babies? Should we grow reserve organs for ourselves, each of us having, as it were, a "savings bank" full of spare kidney, lives or hands? Wild as these notions may sound, every one has its advocates (and opposers) in the scientific community as well as its striking commercial application.-As two critics of genetic engineering, Jeremy Rifkin and Ted Howard, state in their book Who Should Play God'? "Broad Scale genetic engineering will probably be introduced to America much the same way as assembly lines, automobiles, vaccines, computers and all the other technologies. As each new genetic advance becomes commercially practical, a new consumer need will be exploited and a market for the new technology will be created".

单选题A complete change in policy is needed if relations are ever to improve.A. strictB. wideC. everD. radical

单选题An old friend {{U}}called on{{/U}} me the day before yesterday. A.telephoned B.rang C.visited D.saw

单选题Libraries Libraries form a vital part of the world's systems of communication and education. They make available knowledge accumulated through the ages. People in all walks of life use library resources in their work. People also turn to libraries to satisfy a desire for knowledge or to obtain material for leisure-time activity. In addition, many people enjoy book discussions, concerts, film programs, lectures, story hours, and a variety of other activities provided by libraries. Libraries also play an important role in preserving a society's cultural heritage (遗产). The library ranks as one of society's most useful service institutions. The contents of libraries have changed so much through the years that the word library itself is, in a sense, inaccurate. The word comes from the Latin word liber, which means book. Today's libraries house many books, of course. However, they also have a wide variety of other materials that communicate, educate, and entertain. These materials include magazines, manuscripts (手稿), newspapers, and computer documents. Audio and visual materials include CDs, audiocassette tapes, videotapes, films, maps, paintings, and photographs. In addition to regular books, a library may have large-type books, books for the blind, and tape recordings of books, called talking books. Librarians keep pace with the changing contents of libraries to serve as many people as possible. Their efforts have turned libraries into multimedia resource centers. The expansion of library contents greatly increases the library's ability to communicate and educate. For example, people interested in classical music can listen to CDs and read books on the topics. Students of agriculture can read magazines and watch videotapes on farming methods. Many people use magazines and newspapers to find the most up-to-date material on current events. In addition to expanding contents, librarians have developed many kinds of libraries to serve the needs of different people. The materials of each kind of library are selected to meet the needs of a specific group of patrons. School libraries have collections that provide the information needed by elementary and high school students. Public libraries tailor their collections to the general public. Government library collections are geared chiefly toward serving the needs of government officials. Thousands of special libraries provide information for professional people, such as advertising specialists, bankers, editors, engineers, lawyers, physicians, and scientists.

单选题He impressed all his colleagues as a vigorous man in the prime of his career.

单选题He was kept in appalling conditions in prison.

单选题Nerve signals may travel through nerve or muscle fibers at speeds as high as two hundred miles per hour.A. velocitiesB. impulsesC. ratiosD. atrocities

单选题He is a humorous man, especially his expression in his face.A. rationallyB. obviouslyC. particularlyD. traditionally

单选题Accompanied by cheerful music, we began to dance.

单选题Walking to Exercise the Brain Do you think sitting and studying all the time will improve your grades? Think again. Getting some exercise may help, too. New research with older people suggests that taking regular walks helps them pay attention better than if they didn't exercise. Previous research had shown that mice learn, remember, and pay attention better after a few weeks of working out on a running wheel. Mice that exercise have greater blood flow to the brain than those who don't. Their brain cells also make more connections. Neuroscientists from the University at Urbana-Champaign wanted to find out if the same thing is true for people. First, they measured the physical fitness of 41 adults, ages 58 to 77, after each person walked 1 mile. Then, participants looked at arrows on a computer screen and had to use computer keys to show which way one particular arrow was pointing. Adults who were physically fit were faster at the arrow task, and their answers were just as accurate as their less fit peers, the researchers found. The fitter participants also had more blood flow to a part of their brain responsible for paying attention and making decisions. In a second study, 15 elderly people who completed a 6-month aerobic-training course were faster at attention tasks compared with 14 seniors who just did stretching and toning exercises for the same amount of time. So, even going for a walk every 2 or 3 days for just 10 to 45 minutes can help. That should be good news for your grandparents. The effects of exercising on the brains of younger people haven't been studied yet. Still, it can't hurt to take occasional study breaks and go for a walk or run around with your friends. You might even do better in school. Whatever you do, though, don't try to read and walk at the same time. You could end up hurting yourself!

单选题Where Has the Salt Come from? Every now and then, we meet a fact about our earth that makes us feel strange and no answer for the fact has yet been found. Such a fact is the existence of salt in the oceans. How did it get there? We simply do not know how the salt got into the ocean! We do know, of course, that salt is water-soluble, and so passes into the oceans with rainwater. The salt of the earth's surface is constantly being dissolved (溶解) and is passing into the ocean. But we do not know whether this can explain the huge quantity of salt in oceans. If all the oceans were dried up, enough salt would be left to build a wall 180 miles high and a mile thick. Such a wall would reach once around the world at the Equator (赤道)! The common salt that we all use is produced from seawater or the water of salt lakes, from salt springs (源泉) and from deposits of rock salt. The concentration (浓度) of salt in seawater ranges from about three percent to three-and-one-half percent. The Dead Sea, which covers an area of about 340 square miles, contains about 11,600,000,000 tons of salt! On the average, a gallon (加仑) of seawater contains about a quarter of a pound of salt. The beds of rock salt that are found in various parts of the world were all originally formed by the evaporation (蒸发) of seawater millions of years ago. It is believed that the thick rock-salt deposits were formed after about nine-tenth of the volume of seawater had been evaporated. Most commercial salt is obtained from rock salt. The usual method is to drill wells (井) down to the salt beds. Pure water is pumped down (抽进去) through a pipe. The water dissolves the salt and it is forced through another pipe up to the surface.

单选题I don't quite follow what she is saying. A. believe B. understand C. explain D. accept

单选题Guests were scared when the bomb exploded.

单选题The researchers have come up with numerous explanations to ______ their failures.A. excuseB. justifyC. admitD. avoid

单选题Biologists have ascertained that specialized cells convert chemical energy into mechanical energy.

单选题The Development of American Postal System In the early days of the United States, postal charges were paid by the recipient, and charges varied with the distance carried. In 1825, the United States Congress permitted local postmasters to give letters to mail carriers for home delivery, but these carriers received no government salary and their entire compensation depended on what they were paid by the recipients of individual letters. In 1847, the United States Post Office Department adopted the idea of a postage stamp, which of course simplified the payment for postal service but caused grumbling by those who did not like to prepay. Besides, the stamp covered only delivery to the post office and did not include carrying it to a private address. In Philadelphia, for example, with a population of 150,000, people still had to go to the post office to get their mail. The confusion and congestion of individual citizens looking for their letters was itself enough to discourage use of the mail. It is no wonder that, during the years of these cumbersome arrangements, private letter-carrying and express businesses developed. Although their activities were only semi-legal, they thrived, and actually advertised that between Boston and Philadelphia they were half-day speedier than the government mail. The government postal service lost volume to private competition and was not able to handle efficiently even the business it had. Finally, in 1863, Congress provided that the mail carriers who delivered the mail from the post offices to private addresses should receive a government salary, and that there should be no extra charge for that delivery. But this delivery service was at first confined to cities, and free home delivery became a mark of urbanism. In 1890, of the 75 million people in the United States, fewer than 20 million had mail delivered free to their doors. The rest, nearly three quarters of the population, still received no mail unless they went to their post office.

单选题These factors interact {{U}}intimately{{/U}} and cannot be separated.

单选题This kind of material was {{U}}seldom{{/U}} used in building houses during the middle ages.

单选题Plant Gas Scientists have been studying natural sources of methane (甲烷，沼气) for decades but hadn't regarded plants as a producer, notes Frank Keppler, a geochemist(地球化学家) at the Max Planek Institute for Nuclear Physics in Heidelberg, Germany. Now Keppler and his colleagues find that plants, from grasses to trees, may also be sources of the greenhouse gas. This is really surprising, because most scientists assumed that methane production requires an oxygen-free environment. Previously, researchers had thought that it was impossible for plants to make significant amounts of the gas. They had assumed that microbes(微生物) need to be in environments without oxygen to produce methane. Methane is a greenhouse gas, like carbon dioxide. Gases such as methane and carbon dioxide trap heat in Earth's atmosphere and contribute to global warming. In its experiments, Keppler's team used sealed chambers (室，房间；腔) that contained the same concentration of oxygen that Earth's atmosphere has. They measured the amounts of methane that were released by both living plants and dried plant material, such as fallen leaves. With the dried plants, the researchers took measurement at temperatures ranging from 30 degrees Celsius to 70 degrees C..At 30 degrees C., they found, a gram of dried plant material released up to 3 nanograms(微克) of methane per hour (One nanogram is a billionth of a gram. ). With every 10-degree rise in temperature, the amount of methane released each hour roughly doubled. Living plants growing at their normal temperatures released as much as 370 nanograms of methane per gram of plant tissue per hour. Methane emissions tripled (增加三倍) when living and dead plant was exposed to sunlight. Because there was plenty of oxygen available, it's unlikely that the types of bacteria( bacterium 的复数，细菌) that normally make methane were involved. Experiments on plants that were grown in water rather than soil also resulted in methane emissions. That's another strong sign that the gas came from the plants and not soil microbes. The new finding is an "interesting observation," says Jennifer Y.King, a biogeochemist(生物地球化学家) at the University of Minnesota in St. Paul. Because some types of soil microbes consume methane, they may prevent plant-produced methane from reaching the atmosphere. Field tests will be needed to assess the plant's influence, she notes.

单选题Unfortunately war {{U}}started{{/U}} suddenly in the Middle East on October 6, 1973.