39.Among“humanity's current problems” (Line 6, Para. 3), the chief concern of the scientists is _______.

　　A) the impoverishment of developing countries.

　　B) the explosion of the human population.

　　C) the reduction of biological diversity.

　　D) the effect of global warming.

　　注：第三段。C選項中reduction對應rob，diversity對應richness。

　　40.The author's purpose in writing this passage is ________.

　　A) to describe the difficulties in solving humanity's current problems.

　　B) to present the different views on humanity's current problems.

　　C) to analyze the contradiction between countries in dealing with humanity's current problems.

　　D) to point out that humanity's current problems can only be solved through the cooperation of nations.

　　注：看最后一句話，cooperation of nations 對應coordinated international efforts。

　　[Page80]

　　We sometimes think humans are uniquely vulnerable to anxiety, but stress seems to affect the immune defenses of lower animals too. In one experiment, for example, behavioral immunologist (免疫學家)Mark Laudenslger, at the University of Denver, gave mild electric shocks to 24 rats. Half the animals could switch off the current by turning a wheel in their enclosure, while the other half could mot. The rats in the two groups were paired so that each time one rat turned the wheel it protected both itself and its helpless partner from the shock. Laudenslager found that the immune response was depressed below normal in the helpless rats but not in those that could turn off the electricity. What he has demonstrated, he believes, is that lack of control over an event, not the experience itself, is what weakens the immune system.

　　注：1. vulnerable易受傷害的

　　2. immune defense 免疫系統

　　3. found之后是試驗告訴我們的觀點

　　4. depress壓抑，de往下

　　Other researchers agree. Jay Weiss, a psychologist at Duke University School of Medicine, has shown that animals who are allowed to control unpleasant stimuli don't develop sleep disturbances or changes in brain chemistry typical of stressed rats. But if the animals are confronted with situations they have no control over, they later behave passively when faced with experiences they can control. Such findings reinforce psychologists' suspicions that the experience or perception of helplessness is one of the most harmful factors in depression.

　　注：1. 看第一句三個單詞就知道本段內容和上一段相同。

　　2. passive被動的

　　21. Laudenslager's experiment showed that the immune system of those rats who could turn off the electricity ______.

　　A) was strengthened

　　B) was not affected

　　C) was altered

　　D) was weakened

　　注：定位文章第一段found之后