省略If的完全倒装

问题描述:

省略If的完全倒装
Had he known this would happen,he might have acted differently.
为什么用might have现在完成时?
这个虚拟语气有什么格式吗

有固定格式:对现在的虚拟(假设):If条件句谓语动词用一般过去时(be用were);主句用:would/should/might/could+动词原形.对将来的虚拟:If条件句谓语动词可用三种情况:一般过去时,should+动词原形,were to+动词...