单选题"I have great confidence that by the end of the decade we'll know in vast detail how cancer cells arise," says microbiologist Robert Weinberg, an expert on cancer. "But," he cautions, "some people have the idea that once one understands the causes, the cure will rapidly follow. Consider Pasteur, he discovered the causes of many kinds of infections, but it was fifty or sixty years before cures were available." This year, 50 percent of the 910,000 people who suffer from cancer will survive at least five years. In the year 2000 , the National Cancer Institute estimates, that figure will be 75 percent. For some skin cancers, the five-year survival rate is as high as 90 percent. But other survival statistics are still discouraging — 13 percent for lung cancer, and 2 percent for cancer of the pancreas. With as many as 120 varieties in existence, discovering how cancer works is not easy. The researchers made great progress in the early 1970s, when they discovered that oncogenes, which are cancer-causing genes, are inactive in normal cells. Anything from cosmic rays to radiation to diet may activate a dormant oncogene, but how remains unknown. If several oncogenes are driven into action, the cell, unable to turn them off, becomes cancerous. The exact mechanisms involved are still mysterious, but the likelihood that many cancers are initiated at the level of genes suggests that we will never prevent all cancers. "Changes are a normal part of the evolutionary process," says oncologist William Hayward. Environmental factors can never be totally eliminated; as Hayward points out, "We can't prepare a medicine against cosmic rays." The prospects for cure, though still distant, are brighter. "First, we need to understand how the normal cell controls itself. Second, we have to determine whether there are a limited number of genes in cells which are always responsible for at least part of the trouble. If we can understand how cancer works, we can counteract its action."

单选题During his 12 years in Congress he has ______ with the chemical, drug and power companies on behalf of the ordinary person's right to breathe clean air.

单选题A secretary in the future will ______.

单选题America has now adopted more ______ European-style inspection systems, and the incidence of food poisoning is falling.(2014年厦门大学考博试题)

单选题{{B}}Directions:{{/B}} Below each of the following passages you will find some questions or incomplete statements. Each question or statement is followed by four choices marked A, B, C and D. Read each passage carefully, and then select the choice that best answers the question or completes the statement. Mark the letter of your choice with a single bar across the square brackets on your Machine-scoring Answer Sheet.{{B}}Passage One{{/B}} Small, pink and very ugly. Hardly the qualities of a star, but they describe the deformed mouse that was the media darling at a recent science exhibition in Beijing. With a complex tissue structure in the shape of a human ear grafted on to its back, the rosy rodent was a stunning symbol of the serious strides China is making in the field of biotechnology. China is fast applying the latest life-science techniques learned from the West m aggressively pursue genome research. It's establishing its own centers of technical excellence to build a scientific base to compete directly with the United States and Europe. With a plentiful supply of smart young scientists at home and lots of interest abroad biotechnology is on the brink of a boom in China and in the view of foreign scientists, Beijing is playing a clever hand, maximizing the opportunities open to them. For the moment, the cooperation exists mostly with Europe and the U. S. But Asia's other biotech leaders, Japan, Singapore and Korea, also are recognizing China's potential as an attractive low-cost base to conduct research. These partnerships--and China's advancement in the field of biotechnology--could help benefit the rest of Asia: China's rapid progress in improving crop yields will address food-security concerns in the region. In addition, China is more likely to focus on developing cheap technology that its predominantly poor population--and those of other Asian countries--can afford. There remain, however, serious barriers to the development of a strong biotech industry. Among them are a poor domestic legal framework, weak enforcement of intellectual-property rights and loose adherence to international standards. China is a signatory of the International Bio Safety Protocol, which should mean adherence to global standards governing the conduct of field trims. But some observers are skeptical. "The regulations look good, but I haven't met one scientist who believes they are being fully adhered to," says a European science analyst. If shortcuts are taken, then some of the recent scientific achievements trumpeted in the official press may never make it to market. But no matter how strict lab tests are, other problems lie in wait. For example, there is a number of tasks it would take years to fulfill in the patents office, says one lawyer, leaving innovators with little protection if they take a product to market in China.

单选题Peter used to live in London, ______?

单选题Beijing Tourism Bureau has released a list of translations for 2, 753 dishes and drinks to______ public opinions.

单选题On behalf of my company, I am______ to you and your colleagues for your generous help. (2002年清华大学考博试题)

单选题We must take steps now to ______ the survival of these animals.

单选题 Publicly, they are trying to ______ this latest failure, but in private they are very worried.

单选题When her rival died, she ______a grief she did not feel. A. counteracted B. counterchecked C. counterfeited D. counterchanged

单选题My knees were shaking. I (41) afraid (42) with them, (43) I (44) myself out on the path to follow them. Amara's husband (45) coming back and saw me. " (46) my age mates (47) this witchcraft. You come back with me and keep watch (48) my wife. Help me guard (49) body. He will kill her and I cannot prevent it. But he (50) killed her in vain. He shall not eat her body." It was dark inside the reception hut, and very quiet. The women (51) kept watch over Amara, and her co-wife still sat with her. The man stood looking down upon her. A man must never call his wife (52) her name and may never touch her (53) public. The man knelt (54) his wife. "Child of Lam." She did not (55) . Tentatively he (56) his hand on her forehead. Perhaps he thought she heard, (57) he added bravely, " (58) will happen to you, Amara (59) wife.." He clasped her hand in (60) . We sat on in silence waiting for Amara to die.

单选题When a typist gets tired, ______.

单选题In his ______ to further knowledge of the universe, man has now begun to explore space.

单选题When the news of his ______ with the enemy became known, he was hanged in effigy. A. involement B. conversations C. collusion D. complacency

单选题The trucks ______ heavy goods-from factories to the ports.

单选题Even today, (through) the (hustle and bustle) of Nevsky Prospect, St Petersburg's main street, the (classical) beauty of the city (mesmerizes) the eye.