单选题As a ______ major, he enjoyed working in the steel plant. A. metallurgy B. geology C. astronomy D. seismology

单选题At the fall 2001 Social Science History Association convention in Chicago, the Crime and Justice network sponsored a forum on the history of gun ownership, gun use, and gun violence in the United States. Our purpose was to consider how social science history might contribute to the public debate over gun control and gun rights. To date, we have had little impact on that debate. It has been dominated by mainstream social scientists and historians, especially scholars such as Gary Kleck, John Lott, and Michael Bellesiles, whose work, despite profound flaws, is politically congenial to either opponents or proponents of gun control. Kleck and Mark Gertz, for instance, argue on the basis of their widely cited survey that gun owners prevent numerous crimes each year in the United States by using firearms to defend themselves and their property. If their survey respondents are to be believed, American gun owners shot 100,000 criminals in 1994 in self-defense—a preposterous number. Lott claims on the basis of his statistical analysis of recent crime rates that laws allowing private individuals to carry concealed firearms deter murders, ropes, and robberies, because criminals are afraid to attack potentially armed victims. However, he biases his results by confining his analysis to the year between 1977 and 1992, when violent crime rates had peaked and varied little from year to year. He reports only regression models that support his thesis and neglects to mention that each of those models find a positive relationship between violent crime and real income, and an inverse relationship between violent crime and unemployment. Contrary to Kleck and Lott, Bellesiles insists that guns and America's "gun culture" are responsible for America's high rates of murder. In Belleville's opinion, relatively few Americans owned guns before the 1850s or know how to use, maintain, or repair them. As a result, he says, guns contributed little to the homicide rate, especially among white, which was low everywhere, even in the South and on the frontier, where historians once assume guns and murder went hand in hand. According to Bellesiles, these patterns changed dramatically after the Mexican War and especially after the Civil War, when gun ownership became widespread and cultural changes encouraged the use of handguns to command respect and resolve personal and political disputes. The result was an unprecedented wave of gun-related homicides that never truly abated. To this day, the United States has the highest homicide rate of any industrial democracy. Belleville's low estimates of gun ownership in early America conflict, however, with those of every historian who has previously studied the subject and have thus far proven irreproducible. Every homicide statistic he presents is either misleading or wrong. Given the influence of Kleck, Lott, Bellesiles and other partisan scholars on the debate over gun control and gun rights, we felt a need to pull together what social science historians have learned to date about the history of gun ownership and gun violence in America, and to consider what research methods and projects might increase our knowledge in the near future.

单选题The brain is organized into different regions, each responsible for different functions, and in humans this organization is very marked. The largest parts of the brain are the cerebral hemispheres, which occupy most of the interior of the skull. They are layered structures, the most complex being the outer layer, known as the cerebral cortex, where the nerve cells are extremely densely packed to allow great interconnectivity. Its function is not fully understood, but we can get some indication of its purpose from studies of animals that have had it removed. A dog, for example, can still move in a coordinated manner, will eat and sleep, and even bark if it is disturbed. However, it also becomes blind and loses its sense of smell-more significantly, perhaps, it loses all interest in its environment, not responding to people or to its name, nor to other dogs, even of the opposite sex. It also loses all ability to learn. In effect, it loses the characteristics that we generally refer to as indicating intelligence-awareness, interest and interaction with an environment, and an ability to adapt and learn. Thus the cerebral cortex seems to be the seat of the higher order functions of the brain, and the core of intelligence. The cerebral cortex has been the subject of investigation by researchers for many years, and is slowly revealing its secrets. It demonstrates a localization of functions, in that different areas of the cortex fulfill different functions, such as motion control, hearing, and vision. The visual part of the cortex is especially interesting. In the visual cortex, electrical stimulation of the cells can produce the sensation of light, and detailed analysis has shown that specific layers of neurons are sensitive to particular orientations of input stimuli, so that one layer responds maximally to horizontal lines, while another responds to vertical ones. Although much of this structure is genetically pre-determined, the orientation-specific layout of the cells appears to be learnt at an early stage. Animals brought up in an environment of purely horizontal lines do not develop neuron structures that respond to vertical orientations, showing that these structures are developed due to environmental input and not purely from genetic pre-determination. This is called self-organization of the visual cortex since there is no external teacher to guide the development of these structures.

单选题The______of medical knowledge are being pushed farther onwards as time goes on.

单选题Now researchers are directing more attention to the social and cultural impetus that propelled university graduates into careers in management.

单选题______, the market will have to overcome some of the highest hurdles it's seen in a long time.

单选题A scientific law is liable at anytime to need ______; that is an eternal truth. A. modifying B. changing C. revising D. adjusting

单选题Pelter flying across the Atlantic, Charles Lindbergh became famous______.

单选题The problem is that the loss of confidence among the soldiers can be highly contagious. A. spreading B. contemptible C. contented' D. depressing

单选题They suggested that an agency be created to carry out the recommendation of the committee.

单选题We were discussing the housing problem when a middle-aged man cut in and said, "There's no point in talking about impossibilities."

单选题In times of inflation ______.

单选题As he walked out the court, he was ______ with frustration and rage.

单选题His tick convinced none but the most ______. A. credulous B. plausible C. trustworthy D. feasible

单选题Lincoln, former president of the United Stales, is a conspicuous example of a poor boy who succeeded.(2002年中国人民大学考博试题)

单选题With respect to treating chronic Lyme, ______.

单选题An auctioneer likes to get high prices for the goods he sells because ______.

单选题If the test taker finds an item to which an answer is not known, it may be ______ to leave it blank and go on with the test.

单选题{{B}}Passage 1{{/B}} All animals must rest, but do they really sleep as we know it? The answer to this question seems obvious. If an animal regularly stops its activities and stays quiet and unmoving——if it looks as though it is sleeping——then why not simply assume that it is in fact sleeping? But how can observers be sure that an animal is sleeping? They can watch the animal and notice whether its eyes are open or closed, whether it is active or lying quietly, and whether it responds to light or sound. These factors are important clues, but they often are not enough. Horses and cows, for example, rarely close their eyes, and fish and snakes cannot close them. Yet this does not necessarily mean that they do not sleep. Have you ever seen a cat dozing with an eye partly open? Even humans have occasionally been observed to sleep with one or both eyes partially open. Animals do not necessarily lie down to sleep either. Elephants, for example, often sleep standing up, with their tusks resting in the fork of a tree. Finally, while "sleeping" animals often seem unaware of changes in the sounds and light and other stimuli around them, that does not really prove they are sleeping either. Observations of animal behavior alone cannot fully answer the question of whether or not animals sleep. The answers come from doing experiments in sleep laboratories, using a machine called the electroencephalograph (EEC). The machine is connected to animals and measures their brain signals, breathing, heartbeat, and muscle activity. The measurements are different when the animals appear to be sleeping than when they appear to be awake. Using the EEC, scientists have confirmed that all birds and mammals studied in laboratories do sleep. There is some evidence that reptiles, such as snakes and turtles, do not truly sleep, although they do have periods of rest each day, in which they are quiet and unmoving. They also have discovered that some animals, like chimpanzees, cats, and moles (who live underground), are good sleepers while others, like sheep, goats, and donkeys, are poor sleepers. Interestingly, the good sleepers are nearly all hunters with resting places that are safe from their enemies. Nearly all the poor sleepers are animals hunted by other animals: they must always be watching for enemies, even when they are resting.