nominal clause (whether / if (The question is whether it's worth…
whether / if
The question is whether it's worth trying.
Whether she comes or not, makes no difference.
He must answer the question on whether he agrees to it or not.
who, whom, whose, what, which
We're worrying about what we should do next.
No one knows who he was waiting for.
已知: what the teacher is saying...
已知：what is written in the law...
关系词：...what side effects the drug remains
where, when, how, why
What I am anxious to know is when we can visit the museum.
I don't know where we're going to the meeting.