Question

什么情况下宾语从句的引导词 可做宾语从句的主语

什么情况下宾语从句的引导词 可做从句的主语
= = 刚刚还把它和疑问词+不定式弄混了

Answer 1

当它本身就是从句的主语时，这应该很好判断的，从句做主句谓语动词的宾语，但从句动词的主语前没有其他成分，那只能是引导词来做它的主语

Answer 2

只有特殊疑问代词what, which, who 引导宾语从句的同时可以做从句的主语。如：
I don't know what should be done.
Can you tell me which is right?
He told me whom had come to the office.
这些宾语从句有时可以转换成疑问词+不定式：
I don't know what to be done.
不过，当疑问代词在宾语从句中作宾语时，都可以转换成"疑问词+不定式“。如：
I don't know whom I should ask.= I don't know whom to ask.
Can you tell me which I should choose? = Can you tell me which to choose?