41. "Men are naturally most impressed by diseases which have obvious signs," says a wise physician, Dr. Rene Dubos, "yet some of their worst enemies slowly approach them unnoticed."

　　42.Consequently, most of the world's fridges are to be found, not in the tropics where they might prove useful, but in the wealthy countries with mild temperatures where they are climatically almost unnecessary. Every winter, millions of fridges hum away continuously, and at vast expense, busily maintaining an artificially-cooled space inside an artificially-heated house---while outside, nature provides the desired temperature free of charge.

　　43. I think it certain that in decades, not centuries, machines of silicon will arise first to rival and then exceed their human ancestors.

　　44. As the intelligence of robots increases to match that of humans and as their cost declines through economies of scale we may use them to expand our frontiers, first on earth through their ability to withstand environments, harmful to ourselves. Thus, deserts may bloom and the ocean beds be mined. Further ahead, by a combination of the great wealth this new age will bring and the technology it will provide, the construction of a vast, man-created world in space, home to thousands or millions of people, will be within our power.

　　45. Injuries and deaths were relatively less in Los Angeles because the quake occurred at 4.30 a.m. on a holiday, when traffic was light on the city's highways. In addition, changes made to the construction codes in Los Angeles during the last 20 years have strengthened the city's buildings and highways, making them more resistant to quakes.

　　46. The goal was to let farmers precisely target pesticide spraying rather than rain poison on a whole field, which invariable includes plants that don't have pet problems.英语作文
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