问题
选择题
Many human activities also _______carbon gases, which will result in global warming.
A．put off
B．send off
C．let off
D．set off
答案
答案：C
题目分析：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。