1.引导宾语从句。及物动词后的引导词that可省略。
I didn't expect (that) he could win the championship.
The teacher pointed out that Tom was not working hard enough.
2.引导主语从句。通常采用it作形式主语的句型。
That the earth goes around the sun is known to everyone.
（It is known to everyone that the earth goes around the sun.）
3.引导表语从句。
The trouble is that we are short of money.
4.引导同位语从句。
引导同位语从句的`that和引导定语从句的that是不同的。前者只起语法作用，在从句中不作任何成分；而后者在定语从句中作主语、宾语或表语。举例说明：
The news that he resigned from office surprised us.
The idea that he holds is very common nowadays on campus.
