从句：现在（did/were)将来（did、were/should do/were to do)过去（had done)
主句：现在（should、would do/might、could+do）将来（should、would、might、could+do)过去（should、would、might、could+have done）
含蓄虚拟
without.../but for.../otherwise...+would+(not)do/have done)
wish:现在（did、were）过去（have done）将来（would、might、could+do）
would rather：现在/将来（did、were）过去（had done）
If从句虚拟
If the weather were fine now,we would have a picnic(现在）
If it should snow tomorrow,we would go out(将来）
If you had taken my advice,you would not have such a mistake(过去）
下列动词后可用虚拟：should+do（现在/将来）should+be done（过去）
建议 suggest、advice、propose
要求 ask、require、request、demand
其所属的名词形式、形容词形式也用虚拟语气，同样遵循其原则
虚拟语气在名词性从句的应用
It's a pity/a shame/no wonder that(should) do
It's strange/natural/necessary/important/impossible that (should) do
It's desired/suggested/demanded/required that (should)...
It's high/about time that+did 过去/should 现在将来
as if/though+had done过去/did、were现在/would do将来
If only +had done过去/did、were现在/would do将来
省略if：在虚拟条件句中，had/were/should等助动词，可将其提至句首变为倒装句
特殊情况
If you had listened to the doctor,you would be all right now时间错综虚拟
The old lady wasn't told the sad news,or she would have broken down真实虚拟
The manager put forword a suggestion that we had an assistant省略If虚拟
