单选题At some time around 2300BC, give or take a century or two, a large number of the major civilizations of the world collapsed, in Mesopotamia, Egypt, Israel, Anatolia, and Greece, as well as in Afghanistan and China. All of them the first urban civilizations fell into rain at more or less the same time. A thousand years later, around 1200BC, many of the civilizations of the same regions again collapsed at about the same time. The reasons for these widespread and apparently simultaneous disasters which coincided with changes to cultures and societies elsewhere, such as in Britain, have long been a fascinating mystery. Traditional explanations included warfare, famine, and more recently systems collapse, but the apparent absence of direct archaeological or written evidence for causes, as opposed to effects, has led many archaeologists and historians into a resigned assumption that no definite explanation can be found. Over the past 15 years, however, a new type of 'natural disaster' has been proffered which is beginning to be regarded by many scholars as the most probable single explanation for widespread and simultaneous cultural collapse. The new theory has been advanced largely by astronomers and remains largely unknown by archaeologists (notable exceptions include Professor Baillie of Belfast and Dr. Euan Mackie in Glasgow). The theory postulates that the disasters were caused by the impact of comets or other types of cosmic debris on the Earth. French archaeologist Chude Schaeffer, in 1948, published his analysis and compared the destruction layers of more than 40 archaeological sites. He was the first scholar to detect that all of the sites had been totally destroyed several times in the Early, Middle and Late Bronze Age, apparently simultaneously. Since the damage did not show signs of military or other human involvement, and, in any case, was too excessive, he argued that repeated seismic activity might have been responsible. Schaeffer was not taken seriously in 1948, but since then natural scientists have found widespread and unambiguous evidence for abrupt climate change, sudden sea level changes, catastrophic inundations, and seismic activity at several periods since the last Ice Age, particularly around 2300BC. Areas such as the Sahara, which were once farmed, became deserts. Tree rings show disastrous conditions at 2350BC. In Mesopotamia the land appears to have been inundated, devastated, or totally burned. Scholars who, following Schaeffer, favor earthquakes as the principal cause of civilization collapse, argue that the world can expect earthquakes every 1000 ～2000 years, leading to abandonment of sites; while scholars who prefer climate change as the principal cause argue that severe droughts caused agriculture to fail and that .societies inexorably fell apart as a result. The question remained what caused the climate change or the earthquakes. By the late 1970's British astronomers Clube and Napier of Oxford University had begun to investigate cometary impact as the ultimate cause. In 1980, the Nobel prize-winning chemist Luis Alvarez and his colleagues published their paper arguing that a cosmic impact had caused the extinction of the dinosaurs. He showed that large amounts of iridium found in geological layers from the time of the dinosaurs had a cosmic origin. Alvarez's paper stimulated further research by Clube and Napier, Professor Mark Bailey, Duncan Steel and Sir Fred Hoyle. All now support the theory of cometary impact and what is now known as the British School of Coherent Catastrophism.

单选题 More than half of all Jews married in U. S. since 1990 have wed people who aren't Jewish. Nearly 480, 000 American children under the age of ten have one Jewish and one non-Jewish parent. And, if a survey compiled by researchers at the University of California at Los Angeles is any indication, it's almost certain that most of these children will not identify themselves as "Jewish" when they get older. That survey asked college freshmen, who are usually around age 18, about their own and their parents' religious identities. Ninety-three percent of those with two Jewish parents said they thought of themselves as Jewish. But when the father wasn't Jewish, the number dropped to 38 percent, and when the mother wasn't Jewish, just 15 percent of the students said they were Jewish, too. "I think what was surprising was just how low the Jewish identification was in these mixed marriage families." Linda Sax is a professor of education at UCLA. She directed the survey which was conducted over the course of more than a decade and wasn't actually about religious identity specifically. But Professor Sax says the answers to questions about religion were particularly striking, and deserve a more detailed study. She says it's obvious that interfaith marriage works against the development of Jewish identity among children, but says it's not clear at this point why that's the case. "This new study is necessary to get more in-depth about their feelings about their religion. That's something that the study that I completed was not able to do. We didn't have information on how they feel about their religion, whether they have any concern about their issues of identification, how comfortable they feel about their lifelong goals. I think the new study's going to cover some of that," she says. Jay Rubin is executive director of Hillel, a national organization that works with Jewish college students. Mr. Rubin says Judaism is more than a religion, it's an experience. And with that in mind, Hillel has commissioned a study of Jewish attitudes towards Judaism. Researchers will concentrate primarily on young adults, those with two Jewish parents, and those with just one, those who see themselves as Jewish, and those who do not. Jay Rubin says Hillel will then use this study to formulate a strategy for making Judaism more relevant to the next generation of American Jews.

单选题Last year, the crime rate in Chicago has sharply ______. A. declined B. lessened C. descended D. slipped

单选题They ______ for an early end to the fighting which had brought about a great loss to the city.(2009年北京航空航天大学考博试题)

单选题Although states were allowed to coin money Uright/U after the American Revolution, they are not allowed to do so today.

单选题The professor gave ______ instructions for carrying out the research project.

单选题The ______ of finding gold in California attracted a lot of people to settle down there. A. prospects B. speculations C. stakes D. provisions

单选题The traffic was very heavy, ______, and so we arrived after the start of the program.

单选题Composed of song, dance, and personal invective, the old comedy plays also include outspoken political criticism and comment on literary and philosophical topics.

单选题Shopping malls have some advantage in suffering from shorter periods of______business. A. stale B. slack C. ferrous D. abundant

单选题If somebody is ______, he is given a medal or other honor as an official reward for what he has done. A. confirmed B. decorated C. appreciated D. nominated

单选题That battered old hat of his is a ______ joke to all his friends.

单选题 The Commercial Revolution was not confined, of course, to the growth of trade and banking. Included in it also were fundamental changes in methods of production. The system of manufacture developed by the craft guilds in the later Middle Ages was rapidly becoming defunct. The guilds themselves, dominated by the master craftsmen, had grown selfish and exclusive. Membership in them was commonly restricted to a few privileged families. Besides, they were so completely choked by tradition that they were unable to make adjustments to changing conditions. Moreover, new industries had sprang up entirely outside the guild system. Characteristic examples were mining and smelting and the woolen industry. The rapid development of these enterprises was stimulated by technical advances, such as the invention of the spinning wheel and the discovery of a new method of making brass, which saved about half of the fuel previously used. In the mining and smelting industries a form of organization was adopted similar to that which has prevailed ever since. But the most typical form of industrial production in the Commercial Revolution was the domestic system, developed first of all in the woolen industry. The domestic system derives its name from the fact that the work was done in the homes of industrial artisans instead of in the shop of a master craftsman. Since the various jobs in the manufacture of a product were given out on contract, the system is also known as the putting out system. Notwithstanding the petty scale of production, the organization was basically capitalistic. The raw material was purchased by an entrepreneur and assigned to individual worker, each of whom would complete his allotted task for a stipulated payment. In the case of the woolen industry the yam would be given out first of all to the spinners, then to the weavers, fullers, and dyer in succession. When the cloth was finally finished, it would be taken by the clothier and sold in the open market for the highest price it would bring.

单选题Sometimes a dictionary designates a noun as attributive, which Umeans/U that it can be used to describe another noun or name its attributes.

单选题In order to photograph ______ animals, elaborate flashlight equipment is necessary.

单选题It is difficult to Udiscern/U the sample that is on the slide unless the microscope is adjusted properly.