单选题As a result, it is proved to be foolish.A. lovelyB. stupidC. practicalD. useful

单选题New Product Will Save Lives Drinking water that looks clean may still contain bugs (虫子), which can cause illness. A small company called Genera Technologies has produced a testing method in three stages, which shows whether water is safe. The new test shows if water needs chemicals added to it, to destroy anything harmful. It was invented by scientist Dr. Adrian Patton, who started Genera five years ago. He and his employees have developed the test together with a British water company. Andy Headland, Genera"s marketing director, recently presented the test at a conference in the USA and forecast good American sales for it. Genera has already sold 11 of its tests at $ 42,500 a time in the UK and has a further four on order. It expects to sell another 25 tests before the end of March. The company says it is the only test in the UK to be approved by the government. Genera was formed five years ago and until October last year had only five employees; it now employs 14. Mr. Headland believes that the company should make around $19 million by the end of the year in the UK alone.

单选题{{B}}第三篇{{/B}} {{B}}New Attempts to Eradicate AIDS Virus{{/B}} A high-profile attempt to eradicate the AIDS virus in a few patients continues to show promise. But researchers won't know for a year or more whether it will work, scientist David Ho told journalists this Wednesday for the Fourth Conference in Viruses and Infections. "This is a study that's in progress," says Ho, head of the Aaron Diamond AIDS Research Center, New York. The study involves 20 people who started combinations of anti-HIV drugs very early in the course of the disease, within 90 days of their infections. They've been treated for up to 18 months. Four others have dropped out because of side effects or problems complying with the exacting drug system. The drugs have knocked the AIDS virus down to undetectable levels in the blood of all remaining patients. And, in the latest development, scientists have now tested lymph nodes and semen from a few patients and found no virus reproducing there, Ho says. "Bear in mind that undetectable does not equal absent," Ho says. Ho has calculated that the drugs should be able to wipe out remaining viruses — at least from known reservoirs throughout the body — in two to three years. But the only way to prove eradication would be to stop the drugs and see if the virus comes back. On Wednesday,' Ho said he wouldn't ask any patient to consider that step before 2 years of treatment. And he emphasized that he is not urging widespread adoption of such early, aggressive treatment outside of trials. No one knows the long-term risks. But other scientists are looking at similar experiments. A federally funded study will put 300 patients on triple-drug treatments and then see if some responding well after six months can continue to suppress the virus on just one or two drugs, says researcher Douglas Richman of the University of California, San Diego. Some patients in that study also may be offered the chance to stop therapy after 18 months or more, he says.

单选题Why More Fertilizer Harms Plant Diversity The 35-year-old mystery of why fertilizers decrease biodiversity has finally been solved. The secret? They increase competition for sunlight. Adding fertilizers 1o grasslands increases the productivity of plants, but leads to a major drop in biodiversity. The amount of nitrogen(氮) and phosphorus(磷) available to plants has doubled in the last 50 years, but the reason why this has harmed diversity has not been easy to answer. The debate has centred on whether fertilizers increase competition above or below ground-for sunlight or soil resources? To resolve the argument, Yann Hautier and Andy Hector from the University of Zurich, Switzerland built their own experimental plant community from scratch. Hautier's team grew 32 plant communities for tour years, before transferring them to a glass house. Each community comprised four different sets of six species. Half were fertilized, the others were left unfertilized. Half of each of these sets had light added, using a system of three fluorescent tubes that were raised as the canopy grew, while the other half were left to grow in normal light conditions. After two years, the sets that were fertilized in normal light conditions showed a significant increase in productivity anti biomass, but lost around one-third of their species diversity compared to the unfertilized groups. Those that were fertilized and given additional light showed no significant loss of diversity. To uncover whether underground competition for root space had any influence on biodiversity, the team added two new species of plant at the beginning of the second year. The roots of half these plants were contained in plastic tubes, which prevented any below-ground competition: the other half were left exposed. Removing below, ground competition from fertilized plots had no detectable impact on the mortality (死亡率) of the seedlings (幼苗), compared to those that were exposed to full root competition, says Hautier. "In the fertilized groups without additional light, there was no difference with or without the root-tube-they died both ways. Even if we remove competition below ground, these plants are unable to grow. " Drew Purves, a computational ecologist from Microsoft Research Cambridge is impressed with the team's findings. "This is a rare example of a simple experiment providing an unambiguous answer to an important ecological question. If these results are general to temperate grasslands-which seems likely-then we can start to develop more targeted policies to offset (补偿, 抵消) one of the most important sources of diversity loss in grasslands. /

单选题The govemment has protected farmers from damaging drops in grain prices.A. slightB. surprisingC. suddenD. harmful

单选题Why are jade and jade finders mentioned in the passage?

单选题The value of a particular variety of clay for pottery is related to its mineralogical and chemical {{U}}makeup{{/U}}.

单选题This text is too difficult to comprehend. A. understand B. digest C. summarize D. read

单选题One of the Nobel Economics Prize winner once said: "Every leisure act has an economic Upayoff/U for someone."

单选题Almost all economists agree that nations {{U}}gain{{/U}} by trading with one another.

单选题The leader collaborate with you in the project.

单选题Sleep Lets Brain File Memories To sleep. Perchance to file? Findings published online this week by the "Proceedings of the National Academy of Sciences" further support the theory that the brain organizes and stows memories formed during the day while the rest of the body is catching zzz's. Gyorgy Buzsaki of Rutgers University and his colleagues analyzed the brain waves of sleeping rats and mice. Specifically, they examined the electrical activity emanating from the somatosensory neocortex (an area that processes sensory information) and the hippocampus, which is a center for learning and memory. The scientists found that oscillations in brain waves from the two regions appear to be intertwined. So-called sleep spindles (bursts of activity from the neocortex) were followed tens of milliseconds later by beats in the hippocampus known as ripples. The team posits that this interplay between the two brain regions is a key step in memory consolidation. A second study, also published online this week by the "Proceedings of the National Academy" of Sciences", links age-associated memory decline to high glucose levels. Previous research had shown that individuals with diabetes suffer from increased memory problems. In the new work, Antonio Convit of New York University School of Medicine and his collaborators studied 30 people whose average age was 69 to investigate whether sugar levels, which tend to increase with age, affect memory in healthy people as well. The scientists administered recall tests, brain scans and glucose tolerance tests, which measure how quickly sugar is absorbed from the blood by the body's tissues. Subjects with the poorest memory recollection, the team discovered, also displayed the poorest glucose tolerance. In addition, their brain scans showed more hippocampus shrinkage than those of subjects better able to absorb blood sugar. "Our study suggests that this impairment may contribute to the memory deficits that occur as people age." Convit says. "And it raises the intriguing possibility that improving glucose tolerance could reverse some age-associated problems in cognition." Exercise and weight control can help keep glucose levels in check, so there may be one more reason to go to the gym.

单选题Thirst for Oil Worldwide every day, we devour the energy equivalent of about 200 million barrels of oil. Most of the energy on Earth comes from the Sun. In fact enough energy from the Sun hits the planet"s surface each minute to cover our needs for an entire year, we just need to find an efficient way to use it. So far the energy in oil has been cheaper and easier to get at. But as supplies dwindle, this will change, and we will need to cure our addiction to oil. Burning wood satisfied most energy needs until the steam-driven industrial revolution, when energy-dense coal became the fuel of choice. Coal is still used, mostly in power stations, to cover one-quarter of our energy needs, but its use has been declining since we started pumping up oil. Coal is the least efficient, unhealthiest and most environmentally damaging fossil fuel, but could make a comeback, as supplies are still plentiful; its reserves are five times larger than oil"s. Today petroleum, a mineral oil obtained from below the surface of the Earth and used to produce petrol, diesel oil and various other chemical substances, provides around 40% of the world"s energy needs, mostly fuelling automobiles. The US consumes a quarter of all oil, and generates a similar proportion of greenhouse gas emissions. The majority of oil comes from the Middle East, which has half of known reserves. But other significant sources include Russia, North America, Norway, Venezuela and the North Sea. Alaska"s Arctic National Wildlife Refuge could be a major new US source, to reduce reliance on foreign imports. Most experts predict we will exhaust easily accessible reserves within 50 years, though opinions and estimates vary. We could fast reach an energy crisis in the next few decades, when demand exceeds supply. As conventional reserves become more difficult to access others such as oil shales and tar sands may be used instead. Petrol could also be obtained from coal. Since we started using fossil fuels, we have released 400 billion tones of carbon, and burning the entire reserves could eventually raise world temperatures by 13℃. Among other horrors, this would result in the destruction of all rainforests and tile inching of all Arctic ice.

单选题We all think that Mary's husband is a very {{U}}boring{{/U}} person,

单选题The mail I wrote to my mom was delivered this morning. A. received B. lost C. sent D. found

单选题Before herbs were available in supermarkets year-round, herb vinegar was made in the fall.

单选题More than 89 percent of the buildings in Annapolis, Maryland, were erected before the Revolutionary War.

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}}(2002年理工A级阅读理解考题) {{B}}Space-Age Archeology{{/B}} It's a strange partnership, but a very effective one: Satellites and space-shuttle-carried radar are helping archeologists. How? By "seeing" through sand or through treetops to locate important archeological sites. The traditional tools for archeologists are shovels and picks. But high technology is making the archeologist's work and time far more productive. Take for example, the second 1981 flight of the Space Shuttle Challenger. During the mission, a powerful, experimental radar was pointed at a lifeless stretch of desert in Egypt called the Selima Sand Sheet(part of the Sahara Desert). To everyone's surprise, the radar penetrated through the sand to the harder rock beneath. On the surface, there is a little indication that Africa's Sahara Desert was never anything but a desert. When the archeologists studied the radar images, they saw what seemed to be impossible: there was sand-buried landscape that was shaped by flowing water; traces of ancient riverbeds appeared to be over nine miles wide, far wider than most sections of the present-day Nile River. Today, the area is one of the hottest, driest desert in the world. Archeologists dug pits along the old river banks and found clues to the past: stream-rounded pebbles (鹅卵石), Stone-Age axes, broken ostrich (鸵鸟) eggshells, and the shells of land snails. The archeologists were quite pleased with these findings. For years, they'd been finding stone axes scattered through the desert, and couldn't understand why. Now we know that early humans were living on the banks of old rivers, and left their beautiful tools behind. Some are so sharp that you could shave with them. More recently, Landsat 4, a special earth-mapping satellite, aided in the discovery of ancient Mayan ruins in Mexico. Lansat can, with the help of false-color imagery, "see through" much of the area. Armed with these maps, a five-person expedition took to the air in a helicopter. By the end of the second day, the team found a stretch of walled fields that expedition members said look like "old New England fences". They just go on, non-stop, for 40 miles. Later in the week, an ancient village was pinpointed, as was the "lost" city of Oxpemul, once found in the early 1930's but quickly reclaimed by the jungle. The findings made them able to map the extent of the Mayan civilization in about five days. Working on foot, it would have taken at least 100 years.