单选题On the table was a vase filled with
artificial
flowers.
单选题According to the passage, which of the following is true of the small businesses in the US?
单选题The policeman wrote down all the particulars of the accident. A. secrets B. details C. benefits D. words
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 be made to grow in water that has become salty. The pair have 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 100 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 slat 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 resuiting 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 crops 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They voted to abolish the office of second vice-president.
单选题In recent years, there has been an increased awareness of the importance of protecting the environment. The three Rs to keep in mind for a cleaner environment are: reduce, reuse, and recycle. First, reduce how much you use. It means shopping with the environment in mind. Consider the environmental impact of each product before you buy it. Make a list of what you need before you go shopping; this will reduce impulse buying. Buy in bulk - its cheaper and eliminates small containers and excess packaging. Besides, bulk merchandise may be shared with friends or neighbors. You should also avoid buying things that can't by recycled. A shopping list can helpA. find cheaper items.B. reduce impulsive buying.C. eliminate small containers.D. avoid excess packagin
单选题I rarely wear a raincoat because I spend most of my time in a car A. normally B. seldom C. frequently D. usually
单选题The Spanish, French, Dutch, and English all
vied for
North American territory.
单选题Eat More, Weigh Less, Live Longer Clever genetic detective work may have found out the reason why a near-starvation diet prolongs the life of many animals. Ronald Kahn at Harvard Medical School in Boston, U.S. , and his colleagues have been able to extend the lifespan (寿命) of mice by 18 per cent by blocking the rodent's (啮齿动物) increase of fat in specific cells. This suggests that thinness-and not necessarily diet-promotes long life in "calorie (热量卡) restricted" animals. "It's very cool work," says aging researcher Cynthia Kenyon of the University of California, San Francisco. "These mice eat all they want, lose weight and live longer. It's like heaven. " Calorie restriction dramatically extends the lifespan of organisms as different as worms and rodents. Whether this works in humans is still unknown, partly because few people are willing to submit to such a strict diet. But many researchers hope they will be able to trigger the same effect with a drug once they understand how less food leads to a longer life. One theory is that eating less reduces the increase of harmful things that can damage cells. But Kahn's team wondered whether the animals simply benefit by becoming thin. To find out, they used biology tricks to disrupt the insulin (胰岛素) receptor (受体) gene in lab mice-but only in their fat cells. "Since insulin is needed to help fat cells store fat, these animals were protected against becoming fat," explains Kahn. This slight genetic change in a single tissue had dramatic effects. By three months of age, Kahn's modified mice had up to 70 per cent less body fat than normal control mice, despite the fact that they ate 55 per cent more food per gram of body weight. In addition, their lifespan increased. The average control mouse lived 753 days, while the thin rodents averaged a lifespan of 887 days. After three years, all the control mice had died, but one-quarter of the modified rodents were still alive. "That they get these effects by just manipulating the fat cells is controversial," says Leonard Guarente of the Massachusetts Institute of Technology, who studies calorie restriction and aging. But Guarente says Kahn has yet to prove that the same effect is responsible for increased lifespan in calorie-restricted animals. "It might be the same effect or there might be two routes to long life," he points out, "and that would be very interesting. /
单选题Unlike gases, liquids are difficult to compress because there is practically no free space between molecules.A. In contrast toB. Similar toC. More toD. Just as
单选题The normal price of a ticket for an adult is $ 230.A. ordinaryB. properC. fairD. medium
单选题You startled me when you shouted.
单选题She {{U}}exhibited{{/U}} great powers of endurance during the climb.
A. play
B. send
C. show
D. tell
单选题From the beginning, water has furnished mail with a source of food and a highway to travel upon. The first civilizations arose where water was a dominant element in the environment, a challenge to man's ingenuity. The Egyptians invented the 365 - day calendar in response to the Nile's annual flooding. The Babylonians, who were among the most famous law -makers in ancient times, invented laws regulating water usage. Water inspired the Chinese to built a 1,000 - mile canal - a complex system, which, after nearly 2,500 years, remains still practically in use and still commands the astonishment of engineers. But the ancients never found complete solutions to their water problems. The Yellow River is also known as" China's Sorrow" ;it is so unpredictable and dangerous that in a single flood it has caused a million deaths. Floods slowed the great civilization of the Indus River Valley, and inadequate drainage ruined much of its land. Today water dominates man as it always has done. Its presence continues to govern the location of his homes and cities; its violent variability can kill man or his herds or his crops; its routes links him to his fellows; its immense value may add to already dangerous political conflicts. There are many examples of this in our own time. Who of the following were among the most famous law makers?A. The ancient Chinese.B. The ancient Egyptians.C. The ancient Babylonians.D. The ancient Indians.
单选题While
we don"t agree, we continue to be friends.
单选题The State of Marriage Today Is there something seriously wrong with marriage today? During the past 50 years the rate of divorce in the United States has exploded: almost 50% of marriages end in divorce now, and the evidence suggests it is going to get worse. If this trend continues, it will lead to the break up of the family, according to a spokesperson for the National Family Association. Some futurists predict that in 100 years, the average American will many at least four times, and extramarital affairs will be even more common than they are now. But what are the reasons for this, and is the picture really so gloomy? The answer to the first question is really quite simple: marriage is no longer the necessity it once was. the institution of marriage has been based for years partly on economic need. Women used to be economically dependent on their husbands as they usually didn't have jobs outside the home. But with the rising number of women in well-paying jobs, this is no longer the case, so they don't feel that they need to stay in a failing marriage. In answer to the second question, the outlook may not be as pessimistic as it seems, While the rate of divorce has risen, the rate of couples marrying has never actually fallen very much, so marriage is still quite popular. In addition to this. many couples now cohabit and don't bother to marry. These couples are effectively married, but they do not appear in either the marriage or divorce statistics. In fact, more than 50~ of first marriages survive. The statistics are deceptive because there is a higher number of divorces in second and third marriages than in first marriages. So is marriage really an outdated institution? The fact that most people still get married indicates that it isn't. And it is also true that married couples have a healthier life than single people: they suffer less from stress and its consequences, such as heart problems, and married men generally consider themselves more contented than their single counterparts. Perhaps the key is to find out what makes a successful marriage and apply it to all of our relationships!
单选题In a bullfight, it is the movement, not the color, of objects that
arouses
the bull.
单选题I can't {{U}}put up with{{/U}} my neighbor's noise any longer; it's driving me mad.
单选题
Medical Journals
Medical journals are publications that report medical information to physicians
and other health professionals. In the past, these journals
were available only in print. With the development of electronic publishing,
many medical journals now have Web sites on the Internet, and some journals
publish only online. A few medical journals, like the Journal of the
American Medical Association, are considered general medical journals
because they cover many fields of medicine. Most medical journals are specialty
journals that focus on a particular area of medicine. Medical
journals publish many types of articles. Research articles report the results of
research studies on a range of topics varying from the basic mechanisms of
diseases to clinical trials that compare outcomes of different treatments.
Review articles summarize and analyze the information available on a specific
topic based on a careful search of the medical literature.
Because the results of individual research studies can be affected by many
factors, combining results from different studies on the same topic can be
helpful in reaching conclusions about the scientific evidence for preventing,
diagnosing or treating a particular disease. Case conferences and case reports
may be published in medical journals to educate physicians about particular
illnesses and how to treat them. Editorials in medical journals are short essays
that express the views of the authors, often regarding a research or review
article published in the same issue. Editorials provide
perspective on how the current article fits with other information on the same
topic. Letters to the editor provide a way for readers of the medical journal to
express comments, questions or criticisms about articles published in that
journal.
单选题Where Did All the Ships Go? The Bermuda Triangle is one (51) the greatest mysteries of the sea. In this triangular area between Florida, Puerto Rico and Bermuda in Atlantic, ships and airplanes (52) to disappear more often than in (53) parts of the ocean. And they do so (54) leaving any sign of all accident or any dead bodies. It is (55) that Christopher Columbus was the first person to record strange happenings in the area. His compass stopped working, a flame came clown from the sky, and a wave 100 to 200-feet-high carried his ship about a mile away. The most famous disappearance in the Bermuda Triangle was the US Naval Air Flight 19. (56) December 5,1945, five bomber planes carrying 14 men (57) on a training mission from the Florida coast. Later that day, all communications with Flight 19 were lost. They just disappeared without a trace. The next morning, 242 planes and 19 ships took part in the largest air-sea search in history. But they found nothing. Some people blame the disappearances (58) supernatural forces. It is suggested the (59) ships and planes were either transported to other times and places, kidnapped by aliens (60) attacked by sea creatures. There are (61) natural explanations, though. The US Navy says that the Bermuda Triangle is one of two places on earth (52) a magnetic compass points towards true north (63) magnetic north. (64) planes and ships can lose their way if they don't make adjustments. The area also has changing weather and is known (65) its high waves. Storms can turn up suddenly and destroy a plane or ship. Fast currents could then sweep away any trace of an accident.