单选题His novel was adapted for the stage in 1949 as a musical play Uentitled/U as St. Louis woman.

单选题Why can't you stop your {{U}}eternal{{/U}} complaining! A. everlasting B. long C. monotonous D. lengthy

单选题In December 1997, a United Airlines flight hit unexpected rough air,

单选题"Salty" Rice Plant Boosts Harvests British scientists are breeding a new generation of rice plants that will be able to grow in soil containing salt water. Their work may enable abandoned farms to become productive once more. Tim Flowers and Tony Yeo, from Sussex University"s School of Biological Sciences, have spent several years researching how crops, such as rice, could he made to grow in water that has become salty. The pair has recently begun a three-year programme, funded by the Biotechnology and Biological Sciences Research Council, to establish which genes enable some plants to survive salty conditions. The aim is to breed this capability into crops, starting with rice. It is estimated that each year more than 10 million hectares (公顷) of agricultural land are lost because salt gets into the soil and stunts (妨碍生长) plants. The problem is caused by several factors. In the tropics, mangroves (红树林) that create swamps (沼泽) and traditionally formed barriers to sea water have been cut down. In the Mediterranean, a series of droughts have caused the water table to drop, allowing sea water to seep (渗透) in. In Latin America, irrigation often causes problems when water is evaporated (蒸发) by the heat, leaving salt deposits behind. Excess salt then enters the plants and prevents them functioning normally. Heavy concentrations of minerals in the plants stop them drawing up the water they need to survive. To overcome these problems, Flowers and Yeo decided to breed rice plants that take in very little salt and store what they do absorb in cells that do not affect the plants" growth. They have started to breed these characteristics into a new rice crop, but it will take about eight harvests before the resulting seeds are ready to be considered for commercial use. Once the characteristics for surviving salty soil are known, Flowers and Yeo will try to breed the appropriate genes into all manners of drops and plants. Land that has been abandoned to nature will then be able to bloom again, providing much needed food in the poorer countries of the world.

单选题Only a small minority of the mentally ill are {{U}}liable{{/U}} to harm themselves or others. A.easy B.possible C.likely D.difficult

单选题This kind of material was Useldom/U used in building houses during the Middle Ages.

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 on line 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A number of theories have been proposed to explain the situation.A. testedB. suggestedC. usedD. announced

单选题{{B}}第二篇{{/B}} {{B}} Please Fasten Your Seatbelts{{/B}} Severe turbulence (湍流) can kill aircraft passengers. Now, in test flights over the Rocky Mountains, NASA (美国航空航天局) engineers have successfully detected clear-air turbulence up to 10 seconds before an aircraft hits it. Clear-air turbulence often catches pilots by surprise. Invisible to radar, it is difficult to forecast and can hurl (用力抛出去) passengers about the cabin. In December 1997, one passenger died and a hundred others were injured when unexpected rough air caused a United Airlines flight over the Pacific to drop 300 metres in a few seconds. However, passengers can avoid serious injury by fastening their seatbelts. "It is the only antidote (对策) for this sort of thing," says Rod Bogue, project manager at NASA's Dryden Flight Research Center in Edwards, California. The centre's new turbulence detector is based on lidar, or laser radar. Laser pulses are sent ahead of the plane and these are then reflected back by particles in the air. The technique depends on the Doppler effect. The wavelength of the light shifts according to the speed at which the particles are approaching. In calm air, the speed equals the plane's airspeed. But as the particles swirl (打漩) in rough air, their speed of approach increases or decreases rapidly. The rate of change in speed corresponds to the severity (激烈程度) of the turbulence. In a series of tests that began last month, a research jet flew repeatedly into disturbed air over the mountain ridges (山脉) near Pueblo, Colorado. The lidar detector spotted turbulence between 3 and 8 kilometres ahead, and its forecasts of strength and duration corresponded closely with the turbulence that the plane encountered. Bogue says that he had "a comfortable amount of time" to fasten his seatbelt. The researchers are planning to improve the lidar's range with a more powerful beam. The system could be installed on commercial aircraft in the next few years.

单选题The ship left New York on her maiden voyage.

单选题They agreed to settle the dispute by peaceful means.

单选题We all think the prices of the computers will soon plunge .

单选题The room is dim and quiet.

单选题For example, those that had learned the maze six weeks after the injection had three times as much "activity" in their stained cells as those mice that learned the maze eight weeks after injection, when the stained cells were fully mature. Cells examined at less than six weeks' old at the time of learning did not show as much activity as at six weeks, however. According to Frankland, this suggests that when neurons reach six weeks of age they are specifically recruited to form the brain networks that support new memories. According to Fankland, the example shows that neurons in mice's brains are specially recmited WhenA. they are six weeks old.B. they are eight weeks old.C. they are between six and eight weeks old.D. they are less than six weeks ol

单选题The story was very {{U}}touching{{/U}}. A. inspiring B. boring C. absorbing D. moving

单选题I am heartily grateful to your help.

单选题Graphene's super strength lies in the fact that.

单选题In a bullfight, it is the movement, not the color, of objects that {{U}}arouses{{/U}} the bull.

单选题The amount of time spent watching television in the average household in the United States has risen steadily since television sets were introduced in the 1950"s.

单选题Reading Reading involves looking at graphic symbols and formulating mentally the sounds and ideas they represent. Concepts of reading have changed (51) over the centuries. During the 1950's and 1960's especially, increased attention has been devoted to defining and describing the reading process. (52) specialists agree that reading (53) a complex organization of higher mental (54) , they disagree about the exact nature of the process. Some experts, who regard language primarily as a code using symbols to represent sounds, (55) reading as simply the decoding of symbols into the sounds they stand (56) . These authorities (57) that meaning, being concerned with thinking, must be taught independently of the decoding process. Others maintain that reading is inexplicably related to thinking, and that a child who pronounces sounds without (58) their meaning is not truly reading. The reader, (59) some, is not just a person with a theoretical ability to read but one who (60) reads. Many adults, although they have the ability to read, have never read a book in its entirety. But some expert they would not be (61) as readers. Clearly, the philosophy, objectives, methods and materials of reading will depend on the definition one use. By the most (62) and satisfactory definition, reading is the ability to (63) the sound-symbols code of the language, to interpret meaning for various purposes, at various rates, and at various levels of difficulty, and to do (64) widely and enthusiastically. (65) reading is the interpretation of ideas through the use of symbols representing sounds and ideas.