单选题Dr Thomas Starzl, like all the pioneers of organ transplantation, had to learn to live with failure. When he performed the world's first liver transplant 25 years ago, the patient, a three-year-old boy, died on the operating table. The next four patients didn't live long enough to get out of the hospital. But more determined than discouraged, Starzl and his colleagues went back to their lab at the University of Colorado Medical School. They devised techniques to reduce the heavy bleeding during surgery, and they worked on better ways to prevent the recipient's immune system from rejecting the organ — an ever-present risk. But the triumphs of the transplant surgeons have created yet another tragic problem: a severe shortage of donor organs. "As the results get better, more people go on the waiting lists and there's wider disparity between supply and need," says one doctor. The American Council on Transplantation estimated that on any given day 15000 Americans are waiting for organs. There is no shortage of actual organs; each year about 5000 healthy people die unexpectedly in the United States, usually in accidents. The problem is that fewer than 20 percent become donors. This trend persists despite laws designed to encourage organ recycling. Under the federal Uniform Anatomical Gift Act, a person can authorize the use of his organs after death by signing a statement. Legally, the next of kin can veto these posthumous gifts, but surveys indicate that 70 to 80 percent of the public would not interfere with a family member's decision. The biggest roadblock,according to some experts,is that physicians don't ask for donations, either because they fear offending grieving survivors or because they still regard some transplant procedures as experimental. When there aren't enough organs to go around, distributing the available ones becomes a matter of deciding who will live and who will die. Once donors and potential recipients have been matched for body size and blood type,the sickest patients customarily go to the top of the local waiting list. Beyond the seriousness of the patients' condition,doctors base their choice on such criteria as the length of time the patient has been waiting, how long it will take to obtain an organ and whether the transplant team can gear up in time.

单选题Her advice was such a good one ______ we all agreed to accept it. A. so B. and C. that D. as

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单选题In 1957 a doctor in Singapore noticed that hospitals were treating an unusual number of influenza-like cases. Influenza is sometimes called "flu" or a "bad cold". He took samples from the throats of patients, and his hospital was able to find the virus of this influenza. There are three main types of the influenza virus. The most important of these are Type A and B, each of them having several subgroups. With the instrument of the hospital the doctor recognized that the outbreak was due to a virus in Group A, but he did not know the subgroup. Then he reported the outbreak to the World Health Organization in Geneva. W. H. O. published the important news alongside reports of a similar outbreak in Hong Kong, where about 15%～20% of the population had become ill. As soon as the London doctors received the package of throat samples, doctors began the standard tests. They found that by reproducing itself at very high speed, the virus had grown more than a milion times within two days. Continuing their careful tests, the doctors checked the effect of drugs against all the known subgroups of Type A virus. None of them gave any protection. This, then, was something new, a new influenza virus, against which the people of the world had no help whatever. Having found the virus they were working with, the two doctors now dropped it into the noses of some specially selected animals, which got influenza as much as human being did. In a short time the usual signs of the disease appealed. These experiments proved that the new virus was easy to catch, but that it was not a killer. Scientists, like the general public, called it simply Asian Flu. The first discovery of the virus, however, was made in China before the disease had appeared in other countries. Various reports showed that the influenza outbreak started in China, probably in February of 1957. By the middle of March it had spread all over China. The virus was found by Chinese doctors early in March. But China was not a member of the World Health Organization and therefore did not report outbreaks of the disease to it. Not until two months later, when travellers carried the virus into Hong Kong, from where it spread to Singapore, did the news of the outbreak reach the rest of the world. By this time, it was well started on its way around the world. Thereafter, W. H. O.'s weekly reports described the steady spread of this great virus outbreak, which within four months swept through every continent.

单选题According to the author, parents ______.

单选题—What do you usually do at weekends? —Er... I usually ______ some cleaning at home. [A] make [B] take [C] do

单选题 The ocean bottom (a region nearly 2.5 times greater than the total land area of the Earth) is a vast frontier that even today is largely unexplored and uncharted. Until about a century ago, the deep-ocean floor was completely inaccessible, hidden beneath waters averaging over 36,000 meters deep. Totally without light and subjected to intense pressures hundreds of times greater than at the Earth's surface, the deep-ocean bottom is a hostile environment to humans, in some ways as forbid- ding and remote as the void of outer space. Although researchers have taken samples of deep-ocean rocks and sediments for over a century, the first detailed global investigation of the ocean bottom did not actually start until 1968, with the beginning of the National Science Foundation's Deep Sea Drilling Project (DSDP). Using techniques first developed for the offshore oil and gas industry, the DSDP's drill ship, the Glomar Challenger, was able to maintain a steady position on the ocean's surface and drill in very deep waters, extracting samples of sediments and rocks from the ocean floor. The Glomar Challenger completed 96 voyages in a 15-year research program that ended in November 1983, During this time, the vessel logged 600,000 kilometers and took almost 20,000 core samples of seabed sediments and rocks at 624 drilling sites around the world. The Glomar Challenger's core samples have allowed geologists to reconstruct what the planet looked like hundreds of millions of years ago and to calculate what it will probably look like millions of years in the future. Today, largely on the strength of evidence gathered during the Glomar Challenger's voyages, nearly all earth scientists agree on the theories of plate tectonics and continental drift that explain many of the geological processes that shape the Earth. The cores of sediment drilled by the Glomar Challenger have also yielded information critical to understand the world's past climates. Deep-ocean sediments provide a climatic record tracing back hundreds of millions of years, because they are largely isolated from the mechanical erosion and the intense chemical and biological activies that rapidly destroy much land-based evidence of past climates. This record has already provided insights into the patterns and causes of past climatic change information that may be used to predict future climates.

单选题What does the author mean when he interprets the urge for a sharper focus?

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