22. It won(’t) be long before +从句（从句中用一般现在时）不久/很久就要…….
It was (not) long before+从句（从句中用一般过去时）不久/很久才……..
23. Those who………….(从句及主句中谓语动词用复数形式).
Anyone who…………= Whoever………..(从句及主句中谓语动词用单数形式)
24…….主句（一般现在时或过去时）…...when从句….(might / should do 或might / should have done) 表示”对比”,意思为 “本该……(可)而却”,主句中为陈述语气,从句里为虚拟语气,如:
Why are you here when you should be in school?你本该上学的怎么在这儿?
He stopped trying when he might have succeeded .本该已成功了他却停止努力了.
25.There is ./ Sb. have no doubt that………(同位语从句,that不可省略)
There is / Sb. have some doubt whether……..(同位语从句不可用if)
Sb. doubt if / whether…….
Sb. don’t doubt that………