求if、only if 、as if虚拟语气的用法?
问题描述：
求if、only if 、as if虚拟语气的用法?
答
if:从句谓语动词 主句谓语动词与现在事实相反 过去式（be动词用were） Would/could/might/should+do与过去事实相反 Had done Would/could/might/should+have done与将来事实相反 ①过去式 Would/could/might/should+...