虚拟语气中的would/conld/should do/have done 与 did/had done有何区别

前面一部分是用在后面的主句里.后面一部分是用在if条件句里的.
举个例子：
If she had reviewed the text yesterday,she would have passed the exam.如果她昨天复习了课文,她是可以通过考试的.
在例句中,had reviewed用在if条件句中,would have passed用在主句中.