虚拟语气

（笔记）
1， 与现在的事实相反：从句用过去式，主句用would/could/might/should/+动词原形
例如；If I had time ，the classroom would be so clean 如果我有时间，教室将会更加干净。
2， 与过去的事实相反：主句用would/could/should/might/+have+ done , 从句中过去完成时
例如；If I had finished my homework ，I would have passed that test
如果当时我完成了我的做，我就能够通过我的考试了。
3，与将来的事实相反：主句用：should/could/would/might/+动词原形，从句用should do （可能性最大），过去式（可能性一般）were to do （可能性最小）
If it should snow tomorrow，I would make a snowman 如果明天下雪，明天我将对一个雪人
If it snowed tomorrow，I would make a snowman 如果明天下雪，明天我将堆一个雪人
If it were to snow tomorrow ，I would make a snowman 如果明天下雪，我将对一个雪人
虚拟语气的倒装形式
If I had worked hard ，I would have finished it 如果当时我努力工作，我就已经完成它了。
=Had I worked hard ，I would have finished it
If it should snow tomorrow ，I would make a snowman 如果明天下月，我将会对雪人
Should it snow tomorrow ，I would make a snowman
If it were to snow tomorrow ，I would make a snowman
=Were it to snow tomorrow ，I would make a snowman