单选题Her sister urged her to apply for the job.

单选题These are their motives for doing it.

单选题{{B}}第三篇{{/B}} {{B}}Thirst for Oil{{/B}} 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 tonnes 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 the melting of all Arctic ice.

单选题Lead is potentially damaging to children"s health.

单选题These figures do not {{U}}take into account{{/U}} the changes that have taken place in recent years.

单选题Which of the following is discussed in the third paragraph?

单选题I am very {{U}}grateful{{/U}} to you for your assistance.

单选题Until recently, the industry has had little guidance in how to proceed with development without harming wildlife. Regulations are mostly imposed by states or local authorities, whose patchwork guidelines vary from stringent to lax. The Wind Turbine Guidelines Advisory Committee, established in 2007 under the U. S. Fish and Wildlife Service, is proposing federal recommendations to reduce wind development's effect on wildlife. Composed of wind-industry members, wildlife officials, and federal authorities, the committee will present the recommendations to the secretary of the interior for review in October. The recommendations are voluntary, but according to David Stout of the U. S. Fish and Wildlife Service, the guidelines will be" unprecedented in terms of companies agreeing to hold themselves to a higher standard." The Wind Turbine Guidelines Advisory Committee is composed of all the following EXCEPTA. wind-industry members.B. wildlife officials.C. federal authorities.D. David Stout.

单选题Jack packed up all the things he had a accumulated over the {{U}}last{{/U}} ten years. A. future B. far C. past D. near

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, US, and his colleagues have been able to extend the lifespan (寿命) of mice by 18 percent 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 (热量单位，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 percent less body fat than normal control mice, despite the fact that they ate 55 percent 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The ability to contemplate two {{U}}contradictory{{/U}} thoughts at once is said to be a mark of genius.

单选题The last few weeks have been enjoyable

单选题Located in Washington, D. C. , the Library of Congress contains an imposing array of books on every conceivable subject.

单选题There is a famous Ulegend/U here about a strange animal that lives in a cave in the mountains.

单选题请根据短文的内容对每个句子做出判断：如果该句提供的是正确信息，请选择A；如果该句提供的是错误信息，请选择B；如果该句的信息文中没有提及，请选择C。 　　　　　　　　　　　　　　　　　　　　{{B}}Radiocarbon Dating{{/B}} Nowadays scientists can answer many questions about the past through a technique called radiocarbon (放射), or carbon-14, dating. One key to understanding how and why something happened is to discover when it happened. Radiocarbon dating was developed in the late 1940s by physicist Willard F. Libby at the University of Chicago. An atom of ordinary carbon, called carbon-12, has six protons (质子) and six neutrons (中子) in its nucleus(原子核). Carbon-14,or C-14,is a radioactive,unstable form of carbon that has two extra neutrons. It returns to a more stable form of carbon through a process called decay(衰减). This process involves the loss of the extra neutrons and energy from the nucleus. In Libby's radiocarbon dating technique, the weak radioactive emissions (放射)from this decay process are counted by instruments such as a radiation detector and counter. The decay rate is used to determine the proportion of C-14 atoms in the 'sample being dated. Carbon-14 is produced in the Earth's atmosphere when nitrogen(氮)-14,or N-14,interacts with cosmie rays(宇宙射线). Scientists believe since the Earth was formed, the amount of nitrogen in the atmosphere has remained constant. Consequently,C-14 formation is thought to occur at a constant rate. Now the ratio of C-14 to other carbon atoms in the atmosphere is known. Most scientists agree that this ratio is useful for dating items back to at least 50,000 years. All life on Earth is made of organic molecules(分子)that contain carbon atoms coming from the atraosphere. So all living things have about the same ratio of C-14 atoms to other carbon atoms in their tissues(组织). Once an organism(有机体)dies it stops taking in carbon in any form, and the C-14 already ,resent begins to decay. Over time the amount of C-14 in the material decreases, and the ratio of C-14 to other carbon atoms goes down. In terms of radiocarbon dating,the fewer C-14 atoms in a sample,the older that sample is.

单选题{{B}}第二篇{{/B}} "Hidden" Species May Be Surprisingly Common Cryptic(隐蔽的；隐藏的)species -- animals that appear identical but are genetically quite distant --may be much more widespread than previously thought. The findings could have major implications in areas ranging from biodiversity(生物多样性)estimates and wildlife management, to our understanding of infectious diseases and evolution. Reports of cryptic species have increased dramatically over the past two decades with the advent of relatively inexpensive DNA (脱氧核糖核酸) sequencing technology. Markus Pfenninger and Klaus Schwenk, of the Goethe-Universitat in Frankfurt, Germany, analyzed all known data on cryptic animal species and discovered that they are found in equal proportions throughout all major branches of the animal kingdom and occur in equal numbers in all biogeographical(生物地理学的)regions. Scientists had previously speculated that cryptic species were predominantly found in insects and reptiles(爬行动物), and were more likely to occur in tropical rather than temperate(温带的)regions. "Species that are seemingly widespread and abundant could in reality be many different Cryptic species that have low populations and are highly endangered," says Pfenninger. Until the genetic information of all species in at least one taxon(分类单元)is thoroughly studied, no one will know just how many cryptic species exist, "It could be as high as 30%," Pfenninger says. "I'm extremely surprised by their results, " says Alex Smith of the University of Guelph in Ontario, Canada. "It's a call to arms to keep doing the broad kind of genetic studies that we are doing. " Sampling as many individuals as possible, scientists hope to complete work on all fish and birds in another 5 to 10 years. Once either of these taxonomic groups is completed, Pfenninger says researchers will be able to decide how many cryptic species exist throughout the animal kingdom. Examples of cryptic species include the African elephant. A 2001 study found the elephants were actually two genetically distinct, non-interbreeding (非杂交繁殖的) species, the African bush elephant and the African elephant. The species are currently listed as vulnerable and threatened, respectively, by the World Conservation Union (WCU). The reclassifications are more than an academic exercise. They define populations that have evolved independently of each other and whose genetic differences can have significant consequences. In the early 1900s misidentification of mosquito species based on morphology confused: attempts to control malaria(疟疾)in Europe. Ultimately, what was thought to be a single species was actually made up of six sibling(同胞，同属)species, only three of which transmitted the disease." The basic unit in biology is always the species, and you have to know what you are dealing with," Pfenninger says. Much previous research is now no longer used, he says, because it is not clear what species was being studied.

单选题The word “expertise’’ in line 3 could be best replaced by

单选题I will {{U}}take up{{/U}} teaching this September.

单选题下面有3篇短文，每篇短文后有5道题，每题后面有4个选项。请仔细阅读短文并根据短文回答其后面的问题，从4个选项中选择1个最佳答案。{{B}}第一篇{{/B}} "Idle speculation" has no place in science, but "speculation" is its very lifeblood, a wellknown physicist believes. The more fundamental and far-reaching a scientific theory is, the more speculative it is likely to be. It is erroneous to believe that science is only concerned with "pure facts", for mere accumulation of facts is a primitive form of science. A mature science tries to arrange facts in significant patterns to see relationships between previously unrelated aspects 'of the universe. A theory that does not suggest new ways of looking at the universe is not likely to make an important contribution to the development of science. However it is also important that theories are checked by new experiments and observations. Dr. Ovenden discusses recent discoveries in biology, chemistry, and 'physics that give clues to the possibility of life in the solar system and other star systems. He discusses conditions on Mars, Venus, Jupiter, and Saturn, and considers whether or not the same conditions may be found on planets of other stars. Only the planets Venus, Earth, and Mars lie within the temperature zone, about 75,000, 000 miles wide in which life can exist. Venus is covered by a dense layer of clouds which permit no observation of the surface, and the surface temperature of the planet is not known. Mars is colder than Earth, the average temperature being about minus 40 degrees Fahrenheit, compared with plus 59 degrees Fahrenheit as the average for earth. However near the Mars poles during the summer season, temperatures may rise to as much as 70 degrees Fahrenheit, whereas winter temperatures may fall to minus 130 degrees Fahrenheit. Because of the extreme difference in the Martian(火星的) seasons, the only life forms expected to exist, without a built-in(内在的，固有的) temperature control such as warm-blooded animals and humans have, are those which would stay inactive most of the year. Attempts have been made to detect in the spectrum of the dark markings on Mars, the absorption lines due to chlorophyII. So far the test has not succeeded. But the infrared spectrum of the Martian markings has been found to be very similar to the spectrum of earth vegetation when studied at high altitudes.

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 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 10M 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 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.