题目内容
【题目】 If the new safety system _______ to use, the accident would never have happened.
A.had been put
B.were put
C.should be put
D.would be put
【答案】A
【解析】如果新的安全系统被投入使用,这个事故本就不会发生.根据句意可知,考查虚拟语气.跟故去事实相反,从句用had done,主句用would have done,再结合new safety system 是被投入使用,故用had been done,即答案为A.
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