单选题The doctors have abandoned the hope to rescue the old man.

单选题Trying to Find a Partner One of the most striking findings of a recent poll in the UK is that of the people interviewed, one in two believes that it is becoming more difficult to meet someone to start a family with. Why are many finding it increasingly difficult to start and sustain intimate relationships? Does modern life really make it harder to fall in love? Or are we making it harder for ourselves? It is certainly the case today that contemporary couples benefit in different ways from relationships. Women no longer rely upon partners for economic security or status. A man doesn't expect his spouse to be in sole charge of running his household and raising his children. But perhaps the knowledge that we can live perfectly well without a partnership means that it takes much more to persuade people to abandon their independence. In theory, finding a partner should be much simpler these days. Only a few generations ago, your choice of soulmate (心上人) was constrained by geography, social convention and family tradition. Although it was never explicit, many marriages were essentially arranged. Now those barriers have been broken down. You can approach a builder or a brain surgeon in any bar in any city on any given evening. When the world is your oyster (牡蛎), you surely have a better chance of finding a pearl. But it seems that the old conventions have been replaced by an even tighter constraint: the tyranny of choice. The expectations of partners are inflated to an unmanageable degree: good looks, impressive salary, kind to grandmother and right socks. There is no room for error in the first impression. We think that a relationship can be perfect. If it isn't, it is disposable. We work to protect ourselves against future heartache and don't put in the hard emotional labor needed to build a strong relationship. Of course, this is complicated by realities. The cost of housing and child-rearing creates pressure to have a stable income and career before a life partnership.

单选题The sea turtle's natural habitat has been considerably reduced.A. suddenlyB. generallyC. slightlyD. greatly

单选题Radiocarbon Dating 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.

单选题阅读下面的短文，文中有15处空白，没处空白给出了4个选项，请根据短文的内容从4个选项中选择1个最佳答案。 Man and Computer What makes people different from computer programs? What is the missing element that our theories don't yet{{U}} (51) {{/U}}．for? The answer is simple: People read newspaper stories {{U}}(52) {{/U}}．a reason to learn more about what they are interested in. Computers, on the other hand, don't. In fact, computers don't{{U}} (53) {{/U}}． have interests; there is nothing in particular that they are trying to find out when they read. If a computer{{U}} (54) {{/U}}． is to be amodelof story understanding, it should also read for a "purpose". Of course, people have several goals that do not make{{U}} (55) {{/U}}to attribute to computers. One might read a restaurant guide in order to satisfy hunger or entertainment goals, or to {{U}}(56) {{/U}}a good place to go for a business lunch. Computers do not{{U}} (57) {{/U}}, and computers do not have business lunches. However, these physiological and social goals give{{U}} (58) {{/U}}to several intellectual or cognitive(认识的) goals. A goal to satisfy hunger gives rise to goals to find{{U}} (59) {{/U}}about the name of a restaurant which serves the desired type of food, how expensive the restaurant is, the {{U}}(60) {{/U}}of the restaurant, etc. These are goals to{{U}} (61) {{/U}}information or knowledge, what we are calling{{U}} (62) {{/U}}goals. These goals can be held by computers too a computer might "want" to find out the location of a restaurant, and read a guide in order to do so{{U}} (63) {{/U}}the same way as a person might. While such a goal would not{{U}} (64) {{/U}}out of hunger in the case of the computer, it might{{U}} (65) {{/U}}rise out of the "goal" to learn more about restaurants.

单选题Ford"s Assembly Line When it comes to singling out those who have made a difference in all our lives, you cannot overlook Henry Ford. A historian a century from now might well conclude that it was Ford who most influenced all manufacturing, everywhere, even to this day, by introducing a new way to make cars—one, strange to say, that originated in slaughterhouses (屠宰场). Back in the early 1900s, slaughterhouses used what could have been called a "disassembly line". Ford reversed this process to see if it would speed up production of a part of an automobile engine called a magneto (磁力发动机). Rather than have each worker completely assemble a magneto, one of its elements was placed on a conveyer, and each worker, as it passed, added another component to it, the same one each time. Professor David Hounshell of the University of Delaware, an expert on industrial development, tells what happened. "The previous day, workers carrying out the entire process averaged one assembly every 20 minutes. But on that day, on the line, the assembly team averaged one every 13 minutes and 10 seconds per person." Within a year, the time had been reduced to five minutes. In 1913, Ford went all the way. Hooked together by ropes, partially assembled vehicles were towed (拖，拉) past workers who completed them one piece at a time. It wasn"t long before Ford was turning out several hundred thousand cars a year, a remarkable achievement then. And so efficient and economical was this new system that he cut the price of his cars in half, to $260, putting them within reach of all those who, up until that time, could not afford them. Soon, auto makers all over the world copied him. In fact, he encouraged them to do so by writing a book about all of his innovations, entitled Today and Tomorrow . The Age of the Automobile had arrived. Today, aided by robots and other forms of automation, everything from toasters to perfumes is made on assembly lines.

单选题 Egypt Felled by Famine Even ancient Egypt' mighty pyramid builders were powerless in the face of the famine that helped bring down their civilian around 2180 BC. Now evidence gleaned(搜集) from mud deposited by the River Nile suggests that a shift in climate thousands of kilometers to the south was ultimately to blame—and the same or worse could happen today. The ancient Egyptians depended on the Niles annual floods to irrigate their crops. But any change in climate that pushed the African monsoons(季风)southwards out of Ethiopia would have diminished these floods. Dwindling(逐渐变少)rains in the Ethiopian highlands would have meant fewer plants to establish the soil. When rain did fall it would have washed large amounts of soil into the Blue Nile and into Egypt, along with sediment(沉积物)from the White Nile. The Blue Nile mud has a different isotope signature(特征) from that of the White Nile. So by analyzing isotope(同位素；核素) differences in mud deposited in the Nile Delta, Michael Krom of Leeds University worked out what proportion of sediment came from each branch of the river. Krom reasons that during periods of drought, the amount of the Blue Nile mud in the river would be relatively high. He found that one of these periods, from 4,500 to 4,200 years ago, immediately predates the fall of the Egypt's old Kingdom. The weakened waters would have been catastrophic for the Egyptians. Changes that affect food supply don't have to be very large to have a ripple effect in societies, says Bill Ryan of the Lamont Doherty Earth Observatory(天文台) in New York. Similar events today could be even more devastating, says team member Daniel Stanley, a geoarchaeologist(地质考古学家) from the Smithsonian Institution in Washington, D. C. "Anything humans do to shift the climate belts would have an even worse effect along the Nile system because the populations have increased dramatically."

单选题He decided to quit smoking because of his cough.A. give upB. put upC. set upD. take up

单选题In fine days, you"d better open windows to ventilate the room.

单选题What leads to the formation of a black hole?

单选题The population of the island Uconsists/U of equal numbers of men and women.

单选题It is highly unlikely that she will arrive today.

单选题Mary looked pale and weary .

单选题{{B}}第三篇{{/B}} {{B}}Egypt Felled by Famine{{/B}} Even ancient Egypt's mighty pyramid builders were powerless in the face of the famine that helped bring down their civilisation around 2180 BC. Now evidence gleaned from mud deposited by the River Nile suggests that a shift in climate thousands of kilometres to the south was ultimately to blame--and the same or worse could happen today. The ancient Egyptians depended on the Nile's annual floods to irrigate their crops. But any change in climate that pushed the African monsoons southwards out of Ethiopia would have diminished these floods. Dwindling rains in the Ethiopian highlands would have meant fewer plants to stablise the soil. When rain did fall it would have washed large mounts of soil into the Blue Nile and into Egypt, along with sediment from the White Nile. The Blue Nile mud has a different isotope signature from that of the White Nile. So by analysing isotope differences in mud deposited in the Nile Delta, Michael Krom of Leeds University worked out what proportion of sediment came from each branch of the fiver. Krom reasons that during periods of drought, the amount of the Blue Nile mud in the river would be relatively high. He found that one of these periods, from 4,50Oto 4,200 years ago, immediately predates the fall of the Egypt's Old Kingdom. The weakened waters would have been catastrophic for the Egyptians. "Changes that affect food supply don't have to be very large to have a ripple effect in societies," says Bill Ryan of the Lamont Doherty Earth Observatory in New York. "Similar events today could be even more devastating," says team member Daniel Stanley, a geoarchaeologist from the Smithsonian Institutions in Washington, D. C.. "Anything humans do to shift the climate belts would have an even worse effect along the Nile system today because the populations have increased dramatically."

单选题The whale will be fed if he doesn't Uhunt/U for himself.

单选题{{B}}第二篇{{/B}} {{B}} Where Have All the Frogs Gone?{{/B}} In the 1980s, scientists around the world began to notice something strange: Frogs were disappearing. More recent research has shown that many kinds of amphibians (两栖动物) are declining or have become extinct. They have been around for a long time - over 350 million years. Why are they dying out now? Scientists are seriously concerned about this question. First of all, amphibians are an important source of scientific and medical knowledge. By studying amphibians, scientists have learned about new substances that could be very useful for treating human diseases. Further research could lead to many more discoveries, but that will be impossible if the amphibians disappear. The most serious aspect of amphibian loss, however, goes beyond the amphibians themselves. Scientists are beginning to think about what amphibian decline means for the planet as a whole. If the earth is becoming unlivable for amphibians, is it also becoming unlivable for other kinds of animals and human, beings as well? Scientists now believe that amphibian decline is due to several environmental factors. One of these factors is the destruction of habitat, the natural area where an animal lives. Amphibians are very sensitive to changes in their habitat. If they cannot find the right conditions, they will not lay their eggs. These days, as wild areas are covered with houses, roads, farms, or factories, many kinds of amphibians are no longer laying eggs. For example, the arroyo toad (蟾蜍) of southern California will only lay its eggs on the sandy bottom of a slow-moving stream. There are very few streams left in southern California, and those streams are often muddy because of building projects. Not surprisingly, the arroyo toad is now in danger of extinction. There are a number of other factors in amphibian decline. Pollution is one of them. In many industrial areas, air pollution has poisoned the rain, which then falls on ponds and kills the frogs and toads that live there. In farming areas, the heavy use of chemicals on crops has also killed off amphibians. Another factor is that air pollution has led to increased levels of ultraviolet (UV) light. This endangers amphibians, which seem to be especially sensitive to UV light. And finally, scientists have discovered a new disease that seems to be killing many species of amphibians in different parts of the world. All these reasons for the disappearance of amphibians are also good reasons for more general concern. The destruction of land, the pollution of the air and the water, the changes in our atmosphere, the spread of diseases - these factors affect human beings, too. Amphibians are especially sensitive to environmental change. Perhaps they are like the canary (金丝雀) bird that coal miners once used to take down into the mines to detect poisonous gases. When the canary became iii or died, the miners knew that dangerous gases were near and their own lives were in danger.

单选题 Can Buildings Be Designed to Resist Terrorist Attack In the aftermath of the terrorist attack on the World Trade Center, structural engineers are trying hard to solve a question that a month ago would have been completely unthinkable. Can building be designed to withstand catastrophic blasts inflicted by terrorists? Ten days after the terrorist attacks on the twin towers, structural engineers from the University at Buffalo and the Multidisciplinary Center for Earthquake Engineering Research (MCEER) headquartered at UB traveled to ground zero as part of a project funded by the National Science Foundation. Visiting the site as part of an MCEER reconnaissance visit, they spent two days beginning the task of formulating ideas about how to design such structures and searching for clues on how to do so in buildings that were damaged, but still are standing. "Our objective in visiting ground zero was to go and look at the buildings surrounding the World Trade Center, those buildings that are still standing, but that sustained damage," said M. Bruneau, Ph.D. " Our immediate hope is that we can develop a better understanding as to why those buildings remain standing, while our long-term goal is to see whether earthquake engineering technologies can be married to existing technologies to achieve enhanced performance of Buildings in the event of terrorist attacks." he added. Photographs taken by the investigators demonstrate in startling detail the monumental damage inflicted on the World Trade Center towers and buildings in the vicinity. One building a block away from the towers remains standing, but was badly damaged. "This building is many meters away from the World Trade Center and yet we see a column there that used to be part of that building", explained A. Whittaker, Ph. D. "The column became a missile that shot across the road, through the window and through the floor." The visit to the area also revealed some surprises, according to the engineers. For example, the floor framing systems in one of the adjacent buildings was quite rugged, allowing floors that were pierced by tons of falling debris to remain intact. "Highly redundant ductile framing systems may provide a simple, but robust strategy for blast resistance." he added. Other strategies may include providing alternate paths for gravity loads in the event that a load-bearing column fails." We also need a better understanding of the mechanism of collapse" , said A. Whittaker. "We need to find out what causes a building to collapse and how you can predict it." A. Reinhorn, Ph.D. noted that "earthquake shaking has led to the collapse of many buildings in the past. It induces dynamic response and extremely high stresses and deformations in structural components. Solutions developed for earthquake-resistant design may be directly applicable to blast engineering and terrorist-resistant design. Part of our mission now at UB is to transfer these solutions and to develop new ones where none exist at present."

单选题The sensation of a "lump in one's throat" arises from an increased flow of blood into the tissues of the pharynx and larynx. A. explanation B. disease C. feeling D. unpleasantness

单选题The little girl grasped her mother"s hand as she crossed the street.

单选题Messalina"s name has become a byword for notorious behavior.