名词性从句中的连接词有连词that / whether / as if，连接代词what / who/ which / whose / whatever / whoever / whomever / whichever，连接副词where / when / why / how / wherever / whenever。
that they are good at english is known to us all.
the problem is that we don’t have enough money.
she expressed the hope that they would come to china one day.
②宾语从句中的连接词that有时可省有时又不可省，在以下几种情况中that不能省略：（a）当that从句和主句谓语动词之间有插入词语或者从句主语之间有插入语时，that不可省略；（b）当that 从句与另一名词性从句并列作宾语时，that不能省；（c）当that作介词宾语时，that不可省掉。 如：
he judged that,because he was a child, he did not understand
everyone knew what happened and that she was worried.
the reason lies in that she works harder than the others do.
③that从句作主语和宾语 时，可以用it 来替换成以下几种结构表达。
(a)it is clear/certain/likely/true/surprising that… （b）it is a pity/shame/g ood idea/no wonder that ...（c）it is said/reported/ believed/known/thought/suggested that … （d）it seems/happens t hat。如：
it happened that i went out last night.
it is said that china will win in the world cup.
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.
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）
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.
whether the meeting will be put off has not been decided yet.