2、表示与过去事实相反的情况
从句：If+主语+had+done
主句：主语+should/would/might/could+have done
If I had got there earlier,I should/would have met her. 如果我早到那儿，我就会见到她。（事实：去晚了）
She looked at me as if I had been a stranger.她看我的样子好像我是一个陌生人。（事实：我并非陌生人）
3、表示对将来情况的主观推测
从句：①if+主语+were to do （if 表示未来的虚拟语气独有形式，其他如wish， even if等词都没有该形式来表示未来的虚拟语气）
②if+主语+should+do
③if+主语+过去式（be动词用were）
主句：主语+should/would/might/could+do
If he should come here tomorrow,I would talk to him.如果他明天来这儿的话，我就跟他谈谈。（事实：来的可能性很小，不可能）
If there were a heavy snow next Sunday,we would go skating.如果下周日下大雪，我们就去滑冰。（事实：下雪可能性很小，不可能）
4、 有时，虚拟条件句中，结果主句和条件从句的谓语动作若不是同时发生时，虚拟语气的形式应作相应的调整。这种条件句叫错综条件句。
①从句的动作与过去事实相反，而主句的动作与正在发生的事实不符。
If I had worked hard at school,I would be an engineer,too.如果我在学校学习刻苦的话，我现在也会成为一个工程师了
If they had informed us,we would not come here now.如果他们通知过我们的话，我们现在就不会来这里了。
②从句的动作与现在事实相反，而主句的动作与过去事实不符。
If he were free today,we would have sent him to Beijing.如果他今天有空的话，我们就已经派他去北京了。
If he knew her,he would have greeted her.要是他认识她的话，他肯定会去问候她了。
Today’s Wise Words: Do one thing at a time, and do well.
今日名言：一次只做一件事，做到最好。
(责任编辑：医学考研网)
