关于英语那些你不知道的事都在这里
http://m.meten.com/test/quwen.aspx?tid=16-73675-0 大学英语语法总结
一. 四六级中虚拟语气用法的总结 虚拟语气在英语里主要用来表达：
a. 非真实的情景，不可能发生的事，即某种与事实相反或难以实现的情况，或说话人主观愿望。
b. 与客观事实相反地情景， 即强制性虚拟语气，表示建议、命令、劝告这一类的意思上，表示强烈的要求做到、必须做到这样的含义。
c. 虚拟语气的表达形式是通过动词的变化形式表达的， 其特点是主从句时态的不一致， 而且一般有明显得标志。
虚拟语气的考点为：would rather＋that从句＋一般过去时：It is vital／ necessary／ important／ urgent／ imperative／ desirable／ advisable／ natural／ essential＋that＋动词原形；It is time／abouttime／hightime＋that＋一般过去时：proposal／suggestion＋that＋动词原形；lest＋that＋should＋动词原形；if only＋that＋would＋动词原形。
If 句型 (共有三种句型) 非真实条件句
1. 与现在的事实相反：
从句用一般过去时，主句的谓语用would (could, might) ＋动词原形 If I were Bill Gates, I would not work so hard every day. 2. 与过去的事实相反：
从句用过去完成时，主句的谓语用would (could, might) ＋ 现在完成时
If I had gone to America when I graduated from middle school, I would have got my PhD degree. 3. 与将来的事实相反：
从句用should (were to，did) + 动词原形，主句的谓语用would (could, might) ＋动词原形
If it should/were to snow tomorrow, I would go skiing. 注意：
在虚拟语气的从句中，动词'be'的过去时态一律用\，不用was If I were you, I would go to look for him. 如果我是你，就会去找他。 If he were here, everything would be all right. 如果他在这儿，一切都会好的。 虚拟条件句的倒装
虚拟条件句的从句部分如果含有were, should, 或had, 可将if省略，再把were, should或had 移到从句句首，实行倒装。
Were they here now, they could help us.
=If they were here now, they could help us. Had you come earlier, you would have met him =If you had come earlier, you would have met him. Should it rain, the crops would be saved. =Were it to rain, the crops would be saved. 典型例题
_____ to do the work, I should do it some other day. A. If were I B. I were C. Were I D. Was I
答案C. 在虚拟条件状语中如果有were