that ...（C）It is said/reported/ believed/known/thought/suggested that ... （D）It seems/happens that。如：

　　It happened that I went out last night.

　　It is said that China will win in the World Cup.

　　④that和what的区别。

that 引导名词性从句时，在主从句中不以当任何句子成分，也没有任何含义；而what引导名词性从句时，在主从句中都要充当一定的句子成分，what可以分解成定语从句中的先行词 + 关系代词即常说的先行词 + that。如：

　　It's shame that he has made such a mistake. Do what he says.

　　⑤同位语从句与定语从句中that的区别。

同位语从句中的连词that只起连接作用，在从句中不担当任何句子成分；而定语从句中的关系代词that在句中做宾语或主语，宾语与先行词有修饰关系。如果句子是同位语从句，就应用连词that而不能用which.同位语从句一般放在表具体含义的名词后解释名词的含义或内容，如以下名词：news、fact、suggestion、truth、plan、belief、doubt、possibility、idea等，而定语从句只是对先行词的限定和修饰。如：

They expressed the hope that they would come to visit China again.(同位语从句)

The hope she expressed is that they would come to visit China again.（定语从句）

（2）whether和if的用法。

①whether和if在宾语从句中可以互换，但是作介词宾语时连接词一般用whether。如：

　　It all depends on whether they will come back.

　　②后面直接跟or not 时用whether。如：

　　I didn't know whether or not he had arrived in Wuhan.

　　③主语从句表语从句中只能用whether。如：

　　Whether the meeting will be put off has not been decided yet.

　　The question is whether they have so much money.

　　④whether可以引导同位语从句，用以说明前面的名词的内容，if不能。如：

We ought to discuss carefully the question whether we can do

　　it or not.

⑤whether常与or连用表示一种选择，if不能这样用；whether也可与动词不定式连用但if不能。如：