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.

单选题A special feature of the weather in England is that

单选题Founded in 1949, the Fraunhofer Society is now Europe's largest organization for applied technology, and has 59 institutes employing 12,000 people. It continues to grow. Last year it swallowed up the Heinrich Hertz institute for Communication Technology in Berlin. Today, there are seven Fraunhofers in the US and Asia. The Fraunhofer Society has a history of about ______ year(s) till now.A. 60B. 50C. sevenD. one

单选题He made an immense amount of money in business. A. large B. small C. limited D. little

单选题The conference explored the possibility of closer trade links.

单选题If roundworms are removed from the soil and placed in a liquid, they thrash {{U}}helplessly{{/U}} around.

单选题When they built this office block, they gave no Uconsideration/U to people in wheelchairs.

单选题Their style of playing football is utterly different.

单选题All the people Ugathered/U at Mary' s house.

单选题The article sketched the major events of the decade.

单选题I got a note from Moira urging me to get in touch.A. instructingB. pushingC. notifyingD. inviting

单选题The writer mentions "a thief" in the second paragraph

单选题Weed killers must be chosen and applied with great care to avoid damage to adjacent trees and shrubs.

单选题How to Be a Successful Businessperson Have you ever wondered why some people are successful in business and others are not? Here"s a story about one successful businessperson. He started out washing dishes and today he owns 168 restaurants. Zubair Kazi was born in Bhatkal, a small town in southwest India. His dream was to be an airplane pilot, and when he was 16 years old, he learned to fly a small plane. At the age of 23 and with just a little money in his pocket, Mr. Kazi moved to the United States. He hoped to get a job in the airplane industry in California. Instead, he ended up working for a company that rented cars. While Mr. Kazi was working at the car rental (租赁的) company, he frequently ate at a nearby KFC restaurant. To save money on food, he decided to get a job with KFC. For two months, he worked as a cook"s assistant. His job was to clean the kitchen and help the cook. "I didn"t like it," Mr. Kazi says, "but I always did the best I could." One day, Mr. Kazi"s two co-workers failed to come to work. That day, Mr. Kazi did the work of all three people in the kitchen. This really impressed the owners of the restaurant. A few months later, the owners needed a manager for a new restaurant. They gave the job to Mr. Kazi. He worked hard as the manager and soon the restaurant was making a profit. A few years later, Mr. Kazi heard about a restaurant that was losing money. The restaurant was dirty inside and food was terrible. Mr. Kazi borrowed money from a bank and bought the restaurant. For the first six months, Mr. Kazi worked in the restaurant from 8 a.m. to 10 p.m., seven days a week. He and his wife cleaned up the restaurant, remodeled the front of the building, and improved the cooking. They also tried hard to please the customers. If someone had to wait more than ten minutes for their food, Mrs. Kazi gave them a free soda. Before long the restaurant was making a profit. A year later, Mr. Kazi sold his restaurant for a profit. With the money he earned, he bought three more restaurants that were losing money. Again, he cleaned them up, improved the food, and retrained the employees. Before long these restaurants were making a profit, too. Today Mr. Kazi owns 168 restaurants, but he isn"t planning to stop there. He"s looking for more poorly managed restaurants to buy. "I love it when I go to buy a restaurant and find it"s a mess, Mr. Kazi says. "The only way it can go is up."

单选题According to some biologists, the instinct to care for the young is perhaps the most interesting characteristic of animals. A. actually B. surprisingly C. seldom D. possibly