单选题According to the text; virgin-soil epidemics can be distinguished from other catastrophic outbreaks of disease in that virgin-soil epidemics

单选题Because there exist surpluses (e. g. wheat, rice, butter) ,aid programs ______.

单选题The tone of the whole text is

单选题The author implies that the behavior of the dominant male rats is sometimes parallel with that of ______.

单选题Violent criminals with something to hide have more reason than ever to be paranoid about a tap on the shoulder which could send them to jail. Queensland police are working through a backlog of unsolved murders with some dramatic success. Greater cooperation between the public and various law enforcement agencies is playing a role, but new genetic-testing techniques are the real key to providing the vital evidence to mount a prosecution. Evidence left behind at the scene of any murder is guaranteed to outlive the person who left it. A blood, saliva or tissue sample in the size of a pin, kept dry and out of sunlight, will last several thousand years. From it, scientific analysis now can tell accurately the sex of the person who left it. When matched against a sample from a crime suspect, it can indicate with million-to-one certainty whether the samples come from the same source. Only twins share identical DNA. So precise is the technology if the biological parents of a suspect agree to provide a sample, forensic scientists can work out the rest for themselves without cooperation from the suspect. Queensland forensic scientists have been using the DNA testing technology since 1992, and last year they were recognized internationally for their competence in positive individual identification. That is part of the reason 20 of Queensland"s most puzzling unsolved murders dating to 1932 are being ac timely investigated. There also have been several recent arrests for unsolved murders. Forensic evidence was instrumental in charges being laid over the bashing death of waitress Tasha Douty on Brampton Island in 1983. Douty"s blood-splattered, naked body was found on a nude sunbathing beach at Dinghy Bay on the island. Footprints in the sand indicated that the killer had grappled with the 21-year-old mother who had fled up the beach before being caught and beaten to death. According to Leo Freney, the supervising forensic scientist at the John Tonge Centre at Brisbane"s Griffith University, DNA testing has become an invaluable tool for police, its use is in identifying and rejecting suspects. In fact, he says, it eliminates more people than it convicts. " It is easily as good as fingerprints for the purpose of identification, " he says. "In the case of violent crime it is better than fingerprints. You can"t innocently explain things like blood and semen at a crime scene where you may be able to innocently explain fingerprints. " In Queensland, a person who has been arrested on suspicion of an offence can be taken before a magistrate and ordered to provide a sample of body fluid by :force if necessary.

单选题{{B}}Part B{{/B}}{{B}}Directions:{{/B}}In the following text, some sentences have been removed. For Questions 41-45, choose the most suitable one from the list A-G to fit into each of the numbered blanks. There are two extra choices, which do not fit in any of the blanks. Mark your answers on ANSWER SHEET 1. Most people would not object to living a few years longer than normal, as long as it meant they could live those years in good health. Sadly, the only proven way to extend the lifespan of an animal in this way is to reduce its calorie intake. Studies going back to the 1930s have shown that a considerable reduction in consumption ( about 50% ) can extend the lifespan of everything from dogs to nematode worms by between 30% and 70%. Although humans are neither dogs nor worms, a few people are willing to give the calorie-restricted diet a try in the hope that it might work for them, too. But not many—as the old joke has it, give up the things you enjoy and you may not live longer, but it will sure seem as if you did. Now, though, work done by Marc Hellerstein and his colleagues at the University of California, Berkeley, suggests that it may be possible to have, as it were, your cake and eat it too. Or, at least, to eat 95% of it. Their study, to be published in the American Journal of Physiology—Endocrinology and Metabolism, suggests that significant gains in longevity might be made by a mere 5% reduction in calorie intake. The study was done on mice rather than people. But the ubiquity of previous calorie-restriction results suggests the same outcome might well occur in other species, possibly including humans. However, you would have to fast on alternate days.(41)______ Cancer is the uncontrolled growth of cells. For a cancer to develop efficiently, it needs multiple mutations to accumulate in the DNA of the cell that becomes the tumor's ancestor.(42)______ A slower rate of cell division thus results in a slower accumulation of cancer-causing mutations.(43)______ Heavy water is heavy because the hydrogen in it weighs twice as much as ordinary hydrogen (it has a proton and a neutron in its nucleus, instead of just a proton). Chemically, however, it behaves like its lighter relative. This means, among other things, that it gets incorporated into DNA as that molecule doubles in quantity during cell division.(44)______ Dr Hellerstein first established how much mice eat if allowed to feed as much as they want. Then he set up a group of mice that were allowed to eat only 95% of that amount. In both cases, he used the heavy-water method to monitor cell division. The upshot was that the rate of division in the calorie-restricted mice was 37% lower than that in those mice that could eat as much as they wanted--which could have a significant effect on the accumulation of cancer-causing mutations.(45)______ [A] To stop this happening, cells have DNA-repair mechanisms. But if a cell divides before the damage is repaired, the chance of a successful repair is significantly reduced. [B] Bingeing and starving is how many animals tend to feed in the wild. The uncertain food supply means they regularly go through cycles of too much and too little food ( it also means that they are often restricted to eating less than they could manage ff food were omnipresent). [C] But calorie-reduction is not all the mice had to endure. They were, in addition, fed only on alternate days: bingeing one day and starving the next. So, whether modern man and woman, constantly surrounded by food and advertisements for food, would really be able to forgo eating every other day is debatable. [D] Why caloric restriction extends the lifespan of any animal is unclear, but much of the smart money backs the idea that it slows down cell division by denying cells the resources they need to grow and proliferate. One consequence of that slow-down would be to hamper the development of cancerous tumors. [E] So, by putting heavy water in the diets of their mice, the researchers were able to measure how much DNA in the tissues of those animals had been made since the start of the experiment (and by inference how much cell division had taken place), by the simple expedient of extracting the DNA and weighing it. [F] The second reason, according to Elaine Hsieh, one of Dr Hellerstein's colleagues, is that cutting just a few calories overall, but feeding intermittently, may be a more feasible eating pattern for some people to maintain than making small reductions each and every day. [G] At least, that is the theory. Until now, though, no one has tested whether reduced calorie intake actually does result in slower cell division. Dr Hellerstein and his team were able to do so using heavy water as a chemical "marker" of the process.

单选题Goldman might learn a lesson from Google's deal that

单选题The accident drew renewed attention to the popular but (1) A320. It was the first plane Airbus designed using highly computerized systems that are (2) to curb pilot error and allow crews to land (3) autopilot. Now (4) all Airbus planes—from the A320 to the jumbo A340—operate on a " fly by wire" system, which uses electrical impulses (5) cables and pulleys to move the control (6) on the plane's wings. (7) into the plane's software also is a protective "envelope" that limits (8) steeply a pilot can climb, dive or band the aircraft. Still, Airbus has a relatively good safety (9) with A320. Last week's crash was the seventh accident—the fifth resulting in (10) —involving A320 since its (11) in 1987. But some of those accidents have raised the question of whether the aircraft's computer system may be too complicated. Several of the crashes resulted from pilot's making errors in (12) the plane's computerized control or (13) devices. In one (14) 1992 crash near Strassbourg airport, French investigators concluded that an Air Inter plane flew (15) a mountain several miles (16) the runway because the pilots had incorrectly (17) the plane's descent rate into the computer. The cockpit voice recorder showed that up till the moment of (18) , the pilots had no idea of their mistake. (19) , investigators say, such incidents indicate that Airbus may need to add or (20) warning devices that tell the pilots when they are dangerously close to the ground.

单选题On the first Earth Day, the U.S. was a poisoned nation. Dense air pollution blanketed cities like Los Angeles, where smog alerts were a fact of life. Dangerous pesticides like DDT were still in use, and water pollution was rampant—symbolized by raging fires on Cleveland's Cuyahoga River. But the green movement that was energized by Earth Day— and the landmark federal actions that followed it—changed much of that. Today air pollution is down significantly in most urban areas, the water is cleaner, and even the Cuyahoga is home to fish again. But if the land is healing, Americans may be sickening. Since World War Ⅱ, production of industrial chemicals has risen rapidly, and the U.S. generates or imports some 19 billion kg of them per day. These aren't the sorts of chemicals that come to mind when we picture pollution—huge plants spilling contaminated wastewater into rivers. Rather, they're the molecules that make good on the old "better living through chemistry" promise, appearing in items like unbreakable baby bottles and big-screen TVs. Those chemicals have a, habit of finding their way out of everyday products and into the environment—and ultimately into living organisms. A recent biomonitoring survey found traces of 212 environmental chemicals in Americans—including toxic metals, pesticides, etc. "It's not the environment that's contaminated so much," says the director of the Cincinnati Children's Environmental Health Center. "It's us." As scientists get better at detecting the chemicals in our bodies, they're discovering that even tiny quantities of toxins can have a potentially serious impact on our health—and our children's future. Chemicals like bisphenol A (BPA) and phthalates—key ingredients in modern plastics—may disrupt the delicate endocrine system. A host of modern ills that have been rising unchecked for a generation—obesity, diabetes, attention-deficit disorder —could have chemical connections. "We don't give environmental exposure the attention it deserves," says Dr. Philip Landrigan. "But there's an emerging understanding that kids are uniquely susceptible to environmental hazards." Washington has been slow to arrive at that conclusion. The Toxic Substances Control Act (TSCA), the 34-year-old vehicle for federal chemical regulation, has generally been a failure. The burden of proving chemicals dangerous falls almost entirely on the government. And the Environmental Protection Agency (EPA) has been able to issue restrictions on only a handful of chemicals and has lacked the power to ban even some dangerous cancer-causing substances. But change is coming. The Obama Administration is taking a closer look at chemicals. More important, Congress may finally be ready to act. "We can't permit this assault on our children's health—and our own health—to continue," says Senator Frank Lautenberg.

单选题{{B}}Text 4{{/B}} Modem technology may not have improved the world all that much, but. it certainly has made life noisier. Un-muffled motorcycles, blaring car alarms, and roving boom boxes come first, second, and third on my list of most obnoxious noise offenders, but everyone could come up with his own version of aural hell--if he could just find a quiet spot to ponder the matter. Yet what technology has done, other technology is now starting to undo, using computer power to zap those ear-splitting noises into silence. Previously silence seekers had little recourse except to stay inside, close the windows, and plug their ears. Remedies like these are quaintly termed "passive" systems, because they place physical barriers against the unwanted sound. Now computer technology is producing a far more effective "active" system, which doesn't just contain, deflect, or mask the noise but annihilates it electronically. The system works by countering the offending noise with "anti-noise", a some what sinister sounding term that calls to mind antimatter, black holes, and other Popular Science mindbenders but that actually refers to something quite simple. Just as a wave on a pond is flattened when it merges with a trough that is its exact opposite (or mirror image), so can a sound wave by meeting its opposite. This general theory of sound cancellation has been around since the 1930s. In the fifties and sixties it made or a kind of magic trick among laboratory acousticians playing around with the first clunky mainframe computers. The advent of low-cost, high-power microprocessors has made active noise-cancellation systems a commercial possibility, and a handful of small electronics firms in the United States and abroad are bringing the first ones onto the silence market. Silence buffs might be hoping that the noise-canceling apparatus will take the shape of the 44 Magnum wielded by Dirty Harry, but in fact active sound control is not quite that active. The system might more properly he described as reactive in that it responds to sound waves already headed toward human ears. In the configuration that is usual for such systems microphones detect the noise signal and send it to the system's microprocessor, which almost instantly models it and creates its inverse for loudspeakers to fire at the original. Because the two sounds occupy' the same range of frequencies and tones, the inverse sounds exactly tike the noise it is meant to eliminate: the anti-noise canceling Beethoven's Fifth Symphony is heard as Beethoven's Fifth. The only difference is that every positive pressure produced on the air by the orchestra is matched by a negative pressure produced by the computer, and thereby silencing the sound. The system is most effective as a kind of muffler, in which microphones, microprocessor, and loudspeaker are all in a unit encasing the device, that produces the sound, stifling it at its source. But it can work as a headset, too, negating the sound at the last moment before it disturbs one's peace of mind.

单选题Prof. Janet Yellen thinks that Bush's deep tax cuts are

单选题Paragraph 3 is written to

单选题A very important world problem, if not the most serious of all the great world problems which affect us at the moment, is the increasing number of people who actually inhabit this planet. The limited amount of land and land resources will soon be unable to support the huge population if it continues to grow at its present rate. In an early survey conducted in 1888, a billion and a half people inhabited the earth. Now, the population exceeds five billion and is growing fast—by the staggering figure of 90 million in 1988 alone. This means that the world must accommodate a new population roughly equal to that of the United States and Canada every three years! Even though the rate of growth has begun to slow down, most experts believe the population size will still pass eight billion during the next 50 years. So why is this huge Increase in population taking place? It is really due to the spread of the knowledge and practice of what is becoming known as "Death Control". You have no doubt heard of the term "Birth Control"—" Death Control" is something rather different. It recognizes the work of the doctors and scientists who now keep alive people who, not very long ago, would have died of a variety of then incurable diseases. Through a wide variety of technological innovations that include farming methods and sanitation, as well as the control of these deadly diseases, we have found ways to reduce the rate at which we die—creating a population explosion. We used to think that reaching seventy years old was a remarkable achievement, but now eighty or even ninety is becoming recognized as the normal life-span for humans. In a sense, this represents a tremendous achievement for our species. Biologically this is the very definition of success and we have undoubtedly become the dominant animal on the planet. However, this Success is the very cause of the greatest threat to mankind. Man is constantly destroying the very resources which keep him alive. He is destroying the balance of nature which regulates climate and the atmosphere, produces and maintains healthy soils, provides food from the seas, etc. In short, by only considering our needs of today, we are ensuring there will be no tomorrow. An understanding of man' s effect on the balance of nature is crucial to be able to find the appropriate remedial action. It is a very common belief that the problems of the population explosion are caused mainly by poor people living in poor countries who do not know enough to limit their reproduction. This is not true. The actual number of people in an area is not as important as the effect they have on nature. Developing countries do have an effect on their environment, but it is the populations of richer countries that have a far greater impact on the earth as a whole. The birth of a baby in, for example, Japan, imposes more than a hundred times the amount of stress on the world' s resources as a baby in India. Most people in India do not grow up to. own cars or air-conditioners—nor do they eat the huge amount of meat and fish that the Japanese child does. Their life-styles do not require vast quantities of minerals and energy. Also, they are aware of the requirements of the land around them and try to put something back into nature to replace what they take out. For example, tropical forests are known to be essential to the balance of nature yet we are destroying them at an incredible rate. They are being cleared not to benefit the natives of that country, but to satisfy the needs of richer countries. Central American forests are being destroyed for pastureland to make pet food in the United States cheaper; in Papua New Guinea, forests are destroyed to supply cheaper cardboard packaging for Japanese electronic products; in Burma and Thailand, forests have been destroyed to produce more attractive furniture in Singapore and Japan. Therefore, a rich person living thousands of miles away may cause more tropical forest destruction than a poor person living in the forest itself. In short then, it is everybody' s duty to safeguard the future of mankind—not only through population control, but by being more aware of the effect his actions have on nature. Nature is both fragile and powerful. It is very easily destroyed; on the other hand, it can so easily destroy its most aggressive enemy—man.

单选题From the first paragraph of the passage we know that

单选题{{B}}Part A{{/B}}{{B}}Directions:{{/B}} Read the following four texts. Answer the questions below each text by choosing A, B, C or D. Mark your answers on ANSWER SHEET 1. (40 points){{B}}Text 1{{/B}} St. Paul didn't like it. Moses warned his people against it. Hesiod declared it "mischievous" and "hard to get rid of it," but Oscar Wilder said, "Gossip is charming." "History is merely gossip," he wrote in one of his famous plays. "But scandal is gossip made tedious by morality." In past time, under Jewish law, gossipmongers might be fined or flogged. The Puritans put them in stocks or ducking stools, but no punishment seemed to have-the desired effect of preventing gossip, which has continued uninterruptedly across the back fences of the centuries. Today, however, the much-maligned human foible is being looked at in a different light. Psychologists, sociologists, philosophers, even evolutionary biologists are concluding that gossip may not be so bad after all. Gossip is "an intrinsically valuable activity," philosophy professor Aaron Ben-Ze'ev states in a book he has edited, entitled Good Gossip. For one thing, gossip helps us acquire information that we need to know that doesn't come through ordinary channels, such as: "What was the real reason so-and-so was fired from. the office?" Gossip also is a form of social bonding, Dr. Ben-Ze'ev says. It is "a kind of sharing" that also "satisfies the tribal need--namely, the need to belong to and be accepted by a unique group." What's more, the professor notes, "Gossip is enjoyable." Another gossip groupie, Dr. Ronald De Sousa, a professor of philosophy at the University of Toronto, describes gossip basically as a form of indiscretion and a "saintly virtue", by which he means that the knowledge spread by gossip will usually end up being slightly beneficial. "It seems likely that a world in which all information were universally available would be preferable to a world where immense power resides in the control of secrets," he writes. Still, everybody knows that gossip can have its ill effects, especially on the poor wretch being gossiped about. And people should refrain from certain kinds of gossip that might be harmful, even though the ducking stool is long out of fashion. By the way, there is also an interesting strain of gossip called medical gossip, which in its best form, according to researchers Jerry M. Suls and Franklin Goodkin, can motivate people with symptoms of serious illness, but who are unaware of it, to seek medical help. So go ahead and gossip. But remember, if (as often is the case among gossipers) you should suddenly become one of the gossipers instead, it is best to employ the foolproof defense recommended by Plato, who may have learned the lesson from Socrates, who as you know was the victim of gossip spread that he was corrupting the youth of Athens: when men speak ill of thee, so live that nobody will believe them. Or, as Will Rogers said, "Live so that you wouldn't be ashamed to sell the family parrot to the town gossip."