| Over the years, Allan Rechtschaffen has
killed a lot of rats just by keeping them awake. In his sleep laboratory at the University of Chicago, Rechtschaffen places each rat on an enclosed turntable contraption that begins spinning whenever the rodent’s brain waves suggest it is beginning to nod off-forcing the rodent to keep moving so that it doesn’t bump into a wall. After about a week of enforced consciousness, the rat begins showing some signs of strain. Odd lesions break out on its tail and paws. It becomes irritable. Its body temperature drops even as it attempts to make itself warmer than usual. It eats twice as much food as normal but loses 10 to 15 percent of its body weight. After about 17 days of sleeplessness, the rat dies. What kills it "We don’t know," says Rechtschaffen. Thus it goes in the science of sleep. Rats can last A. (A) The Sleep Laboratory at the University of Chicago. B. (B) The Experiment of Rats’ Sleep. C. (C) What is Sleep for D. (D) What can Sleeplessness result in [单项选择]Over the last 40 years there has been a great increase not only in the number of agricultural pesticides in use but also in the care and sophistication with which they are used by farmers. Nevertheless, the proportion of agricultural crops lost to certain pests worldwide has increased over the same period, even when the pests concerned have not developed resistance to existing pesticides.
Which of the following, if true, best explains how improvements in pesticide use have been accompanied by greater losses to certain pests A. Some dangerous but relatively ineffective pesticides common 40 years ago are no longer in widespread use. B. As pesticides have become increasingly pest-specific, controlling certain pests with pesticides has turned out to cost more in many cases than the value of crop losses caused by those pests. C. Because today’s pesticides typically have more specific application conditions than did pesticides in use 40 years ago, today’s farmers observe their fields more closely than did farmers 40 years ago. D. Certain pest-control methods that some farmers use today do not involve the use of chemical pesticides but are just as effective in eliminating insect pests as those that do. E. (E) Forty years ago, much less was known about the effects of pesticides on humans and other mammalian species than is now known. [单项选择]
Over the last 25 years, British society has changed a great deal-or at least many parts of it have. In some ways, however, very little has changed, particularly where attitudes are concerned. Ideas about social class-whether a person is "working-class" or "middle-class"-are one area in which changes have been extremely slow. 我来回答: 提交
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