2015年6月大学英语四级考前模拟试卷及答案五

　　Questions 31 to 35 are based on the following passage.

　　A growing world population and the discoveries of science may alter this pattern of distribution in the future. As men slowly learn to master diseases, control floods, prevent famines, and stop wars, fewer people die every year; and in consequence the population of the world is steadily increasing. In 1925 there were about 2,000 million people in the world; by the end of the century there may well be over 4,000 million.

　　When numbers rise the extra mouths must be fed. New lands must be brought under cultivation, or land already farmed made to yield larger crops. In some areas the accessible land is so intensively cultivated that it will be difficult to make it provide more food. In some areas the population is so dense that the land is parceled out in units too tiny to allow for much improvement in farming methods. Were a large part of this farming population drawn off into industrial occupations, the land might be farmed much more productively by modern methods. There is now a race for science, technology, and industry to keep the output of food rising faster than the number of people to be fed. New strains of crops are being developed which will thrive in unfavorable climates: there are now farms beyond the Arctic Circle in Siberia and North America; irrigation and dry-farming methods bring arid lands under the plough, dams hold back the waters of great rivers to ensure water for the fields in all seasons and to provide electric power for new industries; industrial chemistry provides fertilizers to suit particular soils; aeroplanes spray crops to destroy locusts and many plant diseases. Every year some new means is devised to increase or to protect the food of the world.

　　31. The author says that the world population is growing because _____.

　　A) there are many rich valleys and fertile plains

　　B) the pattern of distribution is being altered

　　C) people are living longer

　　D) new land is being brought under cultivation

　　32. The author says that in densely populated areas the land might be more productively farmed if _____.

　　A) the plots were subdivided

　　B) a large part of the people moved to a different part of the country

　　C) industrial methods were used in farming

　　D) the units of land were made much larger

　　33. We are told that there are now farms beyond the Arctic Circle. This has been made possible by _____.

　　A) producing new strains of crops

　　B) irrigation and dry-farming methods

　　C) providing fertilizers

　　D) destroying pests and disease

　　34. Which of these words is nearest in meaning to the word "strains"

　　A) types B) sizes C) seeds D) harvests

　　35. The author's main purpose is to _____.

　　A) argue for a belief B) describe a phenomenon

　　C) entertain D) propose a conclusion Passage Four

　　Questions 36 to 40 are based on the following passage.

　　For some time past it has been widely accepted that babies-and other creatures-learn to do things because certain acts lead to "rewards"; and there is no reason to doubt that this is true. But it used also to be widely believed that effective rewards, at least in the early stages, had to be directly related to such basic physiological(生理的) "drives" as thirst or hunger. In other words, a baby would learn if he got food or drink or some sort of physical comfort, not otherwise.

　　It is now clear that this is not so. Babies will learn to behave in ways that produce results in the world with no reward except the successful outcome.

　　Papousek began his studies by using milk in the normal way to "reward" the babies and so teach them to carry out some simple movements, such as turning the head to one side or the other. Then he noticed that a baby who had had enough to drink would refuse the milk but would still go on making the learned response with clear signs of pleasure. So he began to study the children's responses in situations where no milk was provided. He quickly found that children as young as four months would learn to turn their heads to right or left if the movement "switched on" a display of lights-and indeed that they were capable of learning quite complex turns to bring about this result, for instance, two left or two right, or even to make as many as three turns to one side.

　　Papousek's light display was placed directly in front of the babies and he made the interesting observation that sometimes they would not turn back to watch the lights closely although they would "smile and bubble" when the display came on. Papousek concluded that it was not primarily the sight of the lights which pleased them, it was the success they were achieving in solving the problem, in mastering the skill, and that there exists a fundamental human urge to make sense of the world and bring it under intentional control.

　　36. According to the author, babies learn to do things which . A) are directly related to pleasure B) will meet their physical needs

　　C) will bring them a feeling of success D) will satisfy their curiosity

　　37. Papousek noticed in his studies that a baby .

　　A) would make learned responses when it saw the milk

　　B) would carry out learned movements when it had enough to drink

　　C) would continue the simple movements without being given milk

　　D) would turn its head to right or left when it had enough to drink

　　38. In Papousek's experiment babies make learned movements of the head in order to .

　　A) have the lights turned on

　　B) be rewarded with milk

　　C) please their parents

　　D) be praised

　　39. The babies would "smile and bubble" at the lights because .

　　A) the lights were directly related to some basic "drives"

　　B) the sight of the lights was interesting

　　C) they need not turn back to watch the lights

　　D) they succeeded in "switching on" the lights

　　40. According to Papousek, the pleasure babies get in achieving something is a reflection of .

　　A) a basic human desire to understand and control the world

　　B) the satisfaction of certain physiological needs

　　C) their strong desire to solve complex problems

　　D) a fundamental human urge to display their learned skills