2. 建筑工程
  3. There is now no doubt that the world is

There is now no doubt that the world is

天天题库2020-05-20  396
问题 There is now no doubt that the world is getting warmer. Data from both the Southern and Northern Hemispheres shows an upward trend in average temperatures over the  1 hundred years. At the moment most scientists are not  2 to stick their necks out and  3  a cause to this trend. It is possible that it represents a natural climatic change caused by a  4 increase in the sun’s  5 output. But these same scientists are  6 aware that recent temperature changes are at the limit of known natural  7 it seems increasingly likely that the  8 is an enhanced greenhouse effect.  The basic theory of the greenhouse effect is quite simple. The earth's atmosphere consists  9 of oxygen and nitrogen, but there are small  10 of various “greenhouse” gases—notably carbon dioxide, water vapor, and methane—which play a very important role in maintaining the planet's “ 11 balance”. As their name suggests these gases have a similar effect to  12  in a greenhouse: they let heat from the sun  13 , and keep it in.  The atmosphere is  14 transparent to the visible solar radiation, which warms the earth (ground or oceans) on which it falls.  15 it has been heated, the earth is warmer than space and  16 energy in the form of invisible long-wave infrared radiation. This  17 for nighttime cooling. Greenhouse gases absorb some of this long-wave radiation, and  18 it in the lower atmosphere.  The gases therefore act rather like a blanket by preventing some infrared radiation from leaving the earth-atmosphere system.  19 certain limits, the more greenhouse gases present, the more infra-red radiation will become  20 , and the higher the surface temperature of the earth.
选项 1.______ A.last B.recent C.late D.latest
答案A
解析只有过去的时间才能看出变化趋势（an upward trend），last“刚过去的”符合题意。recent“近来的，最近的”。late“晚的”。latest“最新的”。
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