问题 选择题

从前的黄土高原有茫茫的林海和无边的草原,而今却成了荒山秃岭,其主要的原因是(    )

A.地球上出现温室效应

B.气候变干燥

C.人类乱砍滥伐导致了生态平衡的失调

D.地壳变迁

答案

答案:C

分析:此题考查对生态系统具有一定的自动调节能力的认识.在一般情况下,生态系统中各种生物的数量和所占的比例是相对稳定的.这说明生态系统具有一定的自动调节能力,但这种调节能力有一定限度的,如果外界干扰超过了这种限度时,生态系统就会遭到破坏.

解答:解:任何生态系统都有自己的自动调节能力,能使它保持一种动态的平衡,但这种自动调节能力是有限的.特别是外界条件干扰超过了这个限度,平衡就被破坏了,黄土高原是我国人口过于集中的地方,由于长期掠夺式开发,乱砍滥伐,植被大量破坏,引起了严重的水土流失和生态平衡失调造成的.

答案:C

单项选择题

Questions 11-15People value money desperately because they value one another desperately; thus the cause of panic in the stock-market plunge is not that people will lose their dollars but that they will lose their sense of community. For the past couple of weeks, the nation has watched itself roll toward ruin because people were losing their money in bales. If one were tasteless enough to ask a big loser what exactly he was losing, he would sputter, "What am I losing My car! My beautiful home! My children’s educations! My clothes! My dinner! My dollars!" They are all true. People have been mourning the passing of their money for all the things that money can do, and what money can do is impressive. Money can build cities, cure diseases, and win wars. The sudden acquisition of the stuff can toss our spirits into the air like a hat.Money can do considerably more. It offers power, an almost unique form of power, not simply because it allows us to acquire and possess things but because it is we who determine its worth; we who say a ruby costs more than an apple; we who decide that a tennis court is more valuable than a book. Paradoxically, money creates a deep sense of powerlessness as well, since technically we cannot provide money for ourselves; someone or something else must do that for us-our employers or, until recently, our stocks. All that, money can do: and when such essential, familiar functions are snatched from one’s life, small wonder that people may grow wild, frantic, and even murderous.What money can do, however, is not the same as what money is. Let’s return for a moment to the theory: people value money because they value one another. In other words, the usefulness of money is directly related to and established by continuous mutual need. People work for money to buy things that other people make or do, things that they cannot or will not make or do for themselves but that they deem necessary for some definition of self-improvement.Abstractly, money is one of the ways, indeed a universally accepted way, by which we make connections. Cash is cold. So the connections may feel cold, but real blood flows through them. These connections constitute one of the central means by which societies cohere; by which they sustain and characterize themselves.When the coin begins to wobble, as it has in the past weeks, a fear seizes the mind that is disorienting. The fear is not merely that of the loss of possessions but of self-possession, which in some sense is bought and sold from person to person in infinite daily bargains. To lose money is frightening. To lose touch with others is more frightening still. Losing touch may cause the panic of the times.

This passage mainly discusses _______.

A.the functions of money

B. the stock-market plunge

C.a new theory of investment

D. a cold characteristic of cash

单项选择题