单选题 Cost as a Factor in Supply In a purely competitive market, the supplier of goods and services has no control over the market price, because he produces too little to influence market conditions. With no difference between his products and the products {{U}} {{U}} 1 {{/U}} {{/U}}his competitors, he will sell nothing if he charges above the market price and he will sell all if he charges at or {{U}} {{U}} 2 {{/U}} {{/U}}the market price. However, in considering the price, he must take the {{U}} {{U}} 3 {{/U}} {{/U}}of production into consideration. There are times when he may be willing to sell below his cost. This might happen when prices tumble for {{U}} {{U}} 4 {{/U}} {{/U}}he believes will be a short time. However, no business person can {{U}} {{U}} 5 {{/U}} {{/U}}to lose money for a prolonged period. He must be constantly {{U}} {{U}} 6 {{/U}} {{/U}}of his costs in relation to the market price if he is to compete successfully and earn a profit. Many people have the impression that as production increases, costs per unit decrease. {{U}} {{U}} 7 {{/U}} {{/U}}mass production has made this true in certain industries and at certain levels of production, {{U}} {{U}} 8 {{/U}} {{/U}}logic and practical experiences have shown that costs per unit begin to rise beyond a certain level of production. Some economists {{U}} {{U}} 9 {{/U}} {{/U}}to this principle as the law of increasing costs. The reason costs rise as production goes up is {{U}} {{U}} 10 {{/U}} {{/U}}. However, it is easy to recognize that as production goes up, the need for additional factors of production will also grow, {{U}} {{U}} 11 {{/U}} {{/U}}competitive bidding in the marketplace for the factors of production. If a producer needs {{U}} {{U}} 12 {{/U}} {{/U}}skilled labor to produce more, and none of this labor is unemployed, the producer will have to get {{U}} {{U}} 13 {{/U}} {{/U}}from other sources. This can be done by {{U}} {{U}} 14 {{/U}} {{/U}}higher wages. Higher bidding would also apply to the other factors of production. We must also recognize that not all labor is equally productive, {{U}} {{U}} 15 {{/U}} {{/U}}not all land is equally fertile and not all ore (矿石) is equally rich in the mineral wanted.

单选题How do you account for your absence from the class this morning? A. explain B. expand C. examine D. review

单选题The storm caused severe damage.

单选题You"ll have to sprint if you want to catch the train.

单选题 阅读下面的短文，文中有15处空白，每处空白给出了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。 {{B}}Gun Rights in the US{{/B}} Immediately after the shooting at Virginia Tech University, Americans gathered to mourn the dead. The president and the state governor both hurried there to share the{{U}} (51) {{/U}}. But the majority of Americans still cling to their right to{{U}} (52) {{/U}}weapons. Strictly speaking, the US is not the only country{{U}} (53) {{/U}}gun violence has destroyed lives, families and communities in everyday circumstance. But the US is one of the{{U}} (54) {{/U}}countries that seems unwilling and politically incapable of doing anything serious to stop it. In countries like Britain and Canada, the government adopted stricter{{U}} (55) {{/U}}control soon after serious gun violence incidents. US leaders, however, are held{{U}} (56) {{/U}}by the gun lobby and the electoral system. The powerful National Rifle Association, the major supporter of gun{{U}} (57) {{/U}}in the US, is too strong for any party to take on. Most Republicans oppose gun controls anyway. {{U}}(58) {{/U}}the years, the Democrats have found that they can either campaign for gun control or win power, not{{U}} (59) {{/U}}; they prefer power. According to the US Bureau of Justice Statistics, firearm incidents accounted{{U}} (60) {{/U}}nine percent of the 4.7 million violent crimes in 2005. So, although opinion polls show most Americans want stricter gun laws, many don't want to give up their arms they{{U}} (61) {{/U}}to protect themselves. Dave Hancock, a Virginia gun lover, is one example. In an interview he said. "If one professor in Virginia incident had been carrying a legal weapon they might have been able to{{U}} (62) {{/U}}all this." In his opinion, the massacre is an argument for more people to carry weapons, not fewer. But at the root of Americans' clinging to the right to bear arms is not just a fear of crime, but a mistrust of{{U}} (63) {{/U}}, commented UK's Guardian newspaper. One Virginia resident, who had a permit to carry a concealed firearm, told the Guardian that it was{{U}} (64) {{/U}}American's responsibility to have a gun. "Each person," he said, "should not rely solely{{U}} (65) {{/U}}the government for protection."

单选题The nocturnal habits and {{U}}mournful{{/U}} cries of owls have made them objects of superstition for some people.

单选题Deport them or not In a country that defines itself by ideals, not by shared blood, who should be allowed to come, work and live here? In the wake of the Sept. 11 attacks these questions have never seemed more pressing. On Dec. 11, 2001, as part of the effort to increase homeland security, federal and local authorities in 14 states staged "Operation Safe Travel" -raids on airports to arrest employees with false identification (身份证明). In Salt Lake City there were 69 arrests. But those captured were anything but terrorists, most of them illegal immigrants from Central or South America. Authorities said the undocumented workers" illegal status made them open to blackmail(讹诈)by terrorists. Many immigrants in Salt Lake City were angered by the arrests and said they felt as if they were being treated like disposable goods. Mayor Anderson said those feelings were justified to a certain extent, "We"re saying we want you to work in these places, we"re going to look the other way in terms of what our laws are, and then when it"s convenient for us, or when we can try to make a point in terms of national security, especially after Sept. 11, then you"re disposable. There are whole families being uprooted for all of the wrong reasons," Anderson said. If Sept. 11 had never happened, the airport workers would not have been arrested and could have gone oil quietly living in America, probably indefinitely. Ana Castro, a manager at a Ben & Jerry"s ice cream shop at the airport, had been working 10 years with the same false Social Security card when she was arrested in the December airport raid. Now she and her family are living under the threat of deportation (驱逐出境). Castro"s case is currently waiting to be settled. While she awaits the outcome, the government has granted her permission to work here and she has returned to her job at Ben & Jerry"s.

单选题The new secretary has written a remarkably concise report only in a few pages but with all the details.

单选题There is always excitement at the Olympic Games when an athlete breaks previous record of performance.A. beatsB. destroysC. maintainsD. defends

单选题Do you follow what I am saying? A. change B. investigate C. write D. understand

单选题Would you bring me some up-to-date catalogues?

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 at 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An exciting and original topic must be any two interests combined.

单选题Hercules was given many difficult tasks because the king wanted to get rid of him.

单选题The leaves of the eucalyptus tree can be used to make a potent antiseptic that kills harmful bacteria in cuts and scrapes.A. naturalB. dangerousC. rareD. tropical

单选题After our computer network stop short for the third time that day, we all went home.

单选题Preserving Nature for Future Demands for stronger protection for wildlife in Britain sometimes hide the fact that similar needs are felt in the rest of Europe. Studies by the Council of Europe, of which 21 countries are members, have shown that 45 per cent of reptile species and 24 per cent of butterflies are in danger of dying out. European concern for wildlife was outlined by Dr. Peter Baum, an expert in the environment and natural resources division of the council, when he spoke at a conference arranged by the administrators of a British national park. The park is one of the few areas in Europe to hold the council"s diploma for nature reserves of the highest quality, and Dr. Peter Baum had come to present it to the park once again. He was afraid that public opinion was turning against national parks, and that those set up in the 1960s and 1970s could not be set up today. But Dr. Baum clearly remained a strong supporter of the view that natural environments needed to be allowed to survive in peace in their own right. "No area could be expected to survive both as a true nature reserve and as a tourist attraction," he went on. "The short-sighted view that reserves had to serve immediate human demands for outdoor recreation should be replaced by full acceptance of their importance as places to preserve nature for the future." "We forget that they are the guarantee of life systems, on which any built-up area ultimately depends," Dr. Baum went on. "We could manage without most industrial products, but we could not manage without nature. However, our natural environment areas, which are the original parts of our countryside, have shrunk to become mere islands in a spoiled and highly polluted land mass. "

单选题Americans may think that “ American culture”

单选题The city center was Uwiped out/U by the bomb.

单选题John Hanson helped draft instructions for Maryland"s delegates to the Stamp Act Congress.