2. 外语
  3. Some greenhouse gases occur naturally in the atmosphere, while others______(由人类的活动造成).

Some greenhouse gases occur naturally in the atmosphere, while others______(由人类的活动造成).

admin2013-05-19  97
问题 Some greenhouse gases occur naturally in the atmosphere, while others______(由人类的活动造成).
选项
答案result from human activities
解析 “由……造成”直接用result from...的主动形式。
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大学英语四级

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