_____ about it earlier, we could have wamed people of the danger.
_____ about it earlier, we could have wamed people of the danger.
A、Would we know
B、Should we know
C、Have we known
D、Had we known
【正确答案】:D
【题目解析】:本题考查if引导的虚拟语气从句的倒装。原句应为If we had known about it earlier, 省略if的倒装句应为:Had we known 
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