请问一句英语 虚拟的用法
问题描述：
请问一句英语 虚拟的用法
The entire building may have been destroyed by the fire ____ the fire department not responded so quickly.
(A) if
(B) had
答案是B,为什么不选A,而选B呢?谢谢!
答
如果选IF
后面从句就不应该用NOT.而应该用didn't
选had是因为后面其实是倒装句.the fire department （had） not responded so quickly.