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.

　　It is estimated that tens of billions of pounds is spent on cigarettes every year in our country, which is a huge waste.

　　4)状语从句(时间，原因，地点，条件，让步，转折等)

　　When the man is enjoying the cigarette, the smoke becomes a monster (怪物) which will devour him.

　　Whatever the reason, there are still some problems with student use of computers.

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