what 引导的从句什么类型

你问的这个问题属于 名词性从句（包括主语从句,宾语从句,表语从句,同位语从句四种）学好这类从句不难,从句都是由原来完整的句子变来的,可以这样学习：
1）陈述句变为名词性从句（4种）,就是在从句前加上that,然后把that+陈述句当成名词用,即可。如：
English is difficult。----> that English is difficult （名词）
That English is difficult is known to all。(主语从句）
I know that English is difficult。(宾语从句）
My point is that English is difficult。(表语从句）
The idea that English is difficult is widely accepted。(同位语从句）
2）一般疑问句变为名词性从句（4种）,在原一般疑问句前加whether,（有时也可用if,需要特殊记忆）疑问句变为陈述语序即可,如：
Do you know him?----> whether you know him (名词）
Whether you know him is a problem。(主语从句）
I don't know whether you know him。(宾语从句）
The problem is whether you know him。(表语从句）
Answer my question whether you know him。(同位语从句）
3）特殊疑问句变为名词性从句,原来的疑问词不变,语序变为陈述句即可,如：
What are you doing?------> what you are doing (名词）
what you are doing atrracts my attention。(主语从句）
I want to know what you are doing。（宾语从句）
The problem is what you are doing。（表语从句）
The fact what you are doing is know to all。（同位语从句）
How 引导主语从句的例子,你自己应该知道了吧?
如：how old are you?how can i get there?
How old you are is very important。
How i can get there is a question。