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.

单选题As the world"s largest grain exporter, the United States has ______ power over the world food distribution system.

单选题Questions 21—24 are based on the following monologue, You now have 15 seconds to read questions 21—24.