1）主语从句
It is common knowledge that honesty is the best policy.
It is well-known that…
It is self-evident/ conceivable / obvious / apparent that…
It goes without saying that… It is universally acknowledged that…
It is / that
2）宾（表）语从句
We cannot understand why he was so cruel to his roommates.
The problem is not who will go, but who will stay.
3）定语从句（限定性和非限定性）
As is shown/ demonstrated/ illustrated/ depicted/ described…in the cartoon/ picture/ graph/ table…,
There are many reasons why I want to study in your university.
