虚拟语气具体用法的讲解

　　后退一步法是指在准确地判断了该句与哪一事实相反后，按虚拟语气的后退一步法处理从句谓语动词的时态。即：在非真实条件状语从句中，谓语动词按正常情况“后退一步”。
也就是：
1 与过去事实相反，在从句中用过去完成时形式表示。
2 与现在事实相反，在从句中用过去一般时形式表示。
3 与将来事实可能相反，在从句中用过去将来时形式表示。　
　主句中则用情态动词would, should, could 等加一个与从句一致的动词形式。
If I had come her yesterday, I would have seen him.
If I were a teacher, I would be strict with my students.
If it should snow tomorrow, they couldn’t go out.
三、would rather ＋从句
在这种结构中，从句的位于动词用过去形式表示虚拟。
　　I would rather you did this instead of me
　
四 宾语从句中的虚拟语气
advise, direct, agree, ask, demand, decide, desire, insist, order, prefer, propose, request, suggest 后的从句
其从句谓语的动词应用：should＋原形动词

1、表示与现在事实相反的情况：从句：主语+过去时 主句：主语+should/would/could/might+do eg：1．If I were you,I would take an umbrella.　　如果我是你,我会带把伞.（事实：我不可能是你） 2．If I knew his te...