Question

如何区分名词性从句中的四种从句？

Answer 1

放在动词前的从句叫做主语从句；
如： What you said is right. (what you said放在谓语动词is之前，是主语从句)
放在及物动词、动词短语或介词后的从句叫做宾语从句；
如：I can't understand what you said. (what you said放在understand之后，是宾语从句)
放在be动词或其它系动词后的叫做表语从句。
如：That's where I disagree.(where I disagree放在系动词is的后面，是表语从句)
跟在一个抽象名词的后面用以说明该名词的内容的从句叫做同位语从句。
如; He gave me an impression that he worked hard.(that he worked hard用以说明impression的内容，是同位语从句)

追问

不同引导词分别在什么情况下使用呢？有什么条件呢？

比如说where,what,which,who……

追答

where在名词性从句中翻译成“……的地方”： I don't know where the temple is.我不知道庙宇在什么地方（庙宇所在的地方）。这里的where the temple is放在动词know的后面充当宾语从句。另一种翻译方式是Where the temple is is unknown to us.这里的Where the temple is放在谓语动词is的前面作主语，是主语从句。
what在名词性从句中翻译成“……的东西/人”：What you said is wrong.你说的（话）是错的。注意what在从句中要充当主语、宾语或表语，如在上句中what就充当said的宾语。
Which在名词性从句中通常充当定语，译为“哪一个……”: I don't know which person is suited for the job.我不知道哪个人适合这份工作。
who: I don't know who is the suitable person for the job.我不知道谁适合这份工作。who在从句中作主语。