Many human activities also carbon gases, which will result in global warming.
A. put off
B. send off
C. let off
D. set off
网友回答
A. put off
B. send off
(答案→)C. let off
D. set off
解析：考查词组：A. put off推迟，B. send off为…送行，寄出，发出，派往C. let off释放，D. set off出发，引发，引爆，句意：很多人类的活动也释放出二氧化碳，这导致全球气温变暖。选C。