A和B都是一样的,B是A的省略形式.
在虚拟条件句中,有时可将虚拟条件句的连词if省略,但此时应用倒装句型,即将从句中的were,should,had 等提到句首.如：
如果她在这里,她也同意的.
If he were here,she would agree too.
→Were she here,she would agree too.
假若明天下雨,我们只好推迟这场比赛.
If it should rain tomorrow,we should have to put off the match.
→Should it rain tomorrow,we should have to put off the match.
要是我们当时早点找到他的话,我们就可以救活他.
If we had found him earlier we could have saved his life.
→Had we found him earlier we could have saved his life.
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