2. 外语
  3. It’s generally agreed that the greatest threat facing the world today is the warming of the earth’s atmosphere, commonly called

It’s generally agreed that the greatest threat facing the world today is the warming of the earth’s atmosphere, commonly called

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问题    It’s generally agreed that the greatest threat facing the world today is the warming of the earth’s atmosphere, commonly called global warming or the greenhouse effect. But what is the cause of the greenhouse effect?
   We have been producing too many of the gases which, when they are released into the earth’s atmosphere, trap heat, and thus raise their temperatures. There are several gases involved, but the main ones are carbon dioxide ( 二氧化碳 ) and chlorofluorocarbons ( 氯氟甲烷 )--often called CFCs. The carbon dioxide comes from burning forests and from burning fossil fuels such as oil and coal. The CFCs are given off by refrigerators and air-conditioning systems. Carbon dioxide is to blame for 56% of the greenhouse effect, and CFCs for 23%.
   The global warming we are experiencing now is only a result of the carbon dioxide and other gases we have dumped into the atmosphere up to the 1960s. In other words, the damage may have already been done. Temperatures are expected to increase by at least 1.3 Celsius degrees by 2030 and 3 degrees by the year 2070.
选项 A、Cause and Effect of Global Warming
B、Damages Done by Global Warming
C、Global Warming and Industrial Development
D、Solution to the Problem of Pollution
答案A
解析 本题询问本文的最佳标题是什么。本文第一段就提出论点，根据原文(36)处可知，即找出全球变暖的原因及其后果，故选A。
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