．条件句中：
If it were not for…；If it hadn’t been for…这两种句型表示“要是没有”,相当于but for
If it had not been for the PLA man,he would not be studying English now.
if…only…（或If only…）表示“要是…就好了”
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They demanded that the aggressor troops (should) be withdrawn immediately.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.
3．名词性从句：
wish that…（hope后的宾语从句不虚拟）
I wish I were as strong as you.
How I wish it wasn’t raining!
would rather/would sooner/had rather that…表示“宁愿”
I would rather they came tomorrow.
I could go myself but I would sooner you went.
I had rather you told him than I did.
It is time/high time that…
It is time we went to bed.
+(should) do：
if only:要是...多好
Examples:
1.If only he had been here.
要是他当时在这儿就好了.
2.I dread the coming exams.If only I could have time to review my lessons.
我对即将到来的考试非常担心.如果我有时间复习该有多好啊.
3.If only I had another chance.
要是我再有一次机会就好了.
4.I am so tired.If only I can take the day off tomorrow.
太疲倦了.如果明天能不上班多好.
5.If only problems would come one at a time!
要是问题一次只发生一个该多好!
6.If only it clears up,we'll go.
只要天一放晴,我们就去.
7.If only one had an unlimited supply of money!
要是财源不断就好了!
8.She would be a very good player if only she could get it together.