请问,什么从句可以用不定式来替换,分别是怎么替换的.请分别详细举例,谢谢!

这种情况通常是将特殊疑问词引导的名词性从句替换为特殊疑问词+不定时.
具体情况和例句如下：
who what which when where how后加不定式在句中可以做主语、宾语、表语等,但why后加动词原型,是特例:
1.主语
e.g.when we will start has not been decided.可替换为When to start has not been decided.
何时动身还未决定.
2.宾语
e.g.He did not know whether he should go there or not.替换为 He did not know whether to go there or not.
他不知该不该去那.
3.表语
e.g.The difficulty was how we could cross the river.替换为The difficulty was how to cross the river.
困难在于怎样过河.
e.g.The question was where we should go.替换为The question was where to go.
问题是去哪里?
4.双重宾语
e.g.I can tell you where you can get this book.替换为I can tell you where to get this book.
我能告诉你从哪搞到这本书.
e.g.I asked him how I could learn English.替换为I asked him how to learn English.
我告诉他怎样学好英语.
5.有时疑问词前可用介词
e.g.I have no idea of how Ican do it.替换为 I have no idea of how to do it.