三种情况，(1)对过去，从句had done主句would/could/might/have done(2)对现在，从句：did /were主句：would/could/might do(3)对将来，should do/were to do/did.从句，更上一个一样。注意，“主将从现”原则。
1．名词性从句：
demand/suugest/order/insist/propose/request/ask/advise/prefer/command/desire that…
They demanded that the aggressor troops (should) be withdrawn immediately.
由insist引导的宾语从句可以虚拟也可以不虚拟：
He insisted that he was right.坚持认为
He insisted that we should agree with him.坚持某事
由suggest引导的宾语从句可以虚拟也可以不虚拟：
His white face suggests that his not healthy.表明
He suggested that we have a rest.建议
If I could only see him once!
If only I had listened to your advice. 很明显，这种句型省略了主句
2．其他状语从句中：
as if/as though/even if…
Tom looked sad as if he had heard bad news.
I won’t lend you any money even I had money.