自考《英语语法》复习指导：十三 虚拟语气
类别 用法 例句
if引导的条件从句 与现在事实相反 从句动词：过去式（be用were）
主句动词：should/would/could/might+动词原形 if he were here, he would help us.
与过去事实相反 从句动词：had+过去分词
主句动词：should/would/could/might+have+过去分词 if i had been free, i would have visited you.
与将来事实相反 从句动词：过去式 / should+动词原形 / were+不定式
主句动词：should/would/could/might+动词原形 if it should rain tomorrow, we would not go camping.
其它状语从句 as if引导的状语从句中动词用过去式或过去完成式 they are talking as if they had been friends for years.
in order that / so that引导的状语从句中动词用can / could / may / might / would等+动词原形 turn on the light so that we can see it clearly.
宾语从句 demand, suggest, order, insist后接的从句中动词为should+动词原形 he suggested that we not change our mind.
wish后的从句中分别用过去式，过去完成式和should/would+动词原形表示与现在，过去和将来情况相反 i wish i could be a pop singer.
主语从句 在it is necessary / important / strange that…, it is suggested / demanded / ordered / requested that… 等从句中，谓语动词用should+动词原形 it is strange that such a person should be our friends.
其它句型中 it is time that…句型中动词用过去式或should+动词原形 it’s high time that we left.
would rather所接的从句中动词用过去式或者过去完成式 i would rather you stayed at home now.
if only句型中动词常用过去式或者过去完成式，表示强烈的愿望 if only our dream had come true!