⑵ 当主句的谓语动词与 that 宾语从句之间有插入语时，that一般不可省。

如：Just then I noticed for the first time,that our master was wearing

his fine green coat and his black silk cap.

⑶ 当that 从句是双宾语中的直接宾语时，that不可省。

如：I can't tell him that his mother died.

注意：许多带复合宾语的句子，that引导的宾语从句经常移到句子后部，而用it作形式宾语。

如：I find it necessary that we should do the homework on time.

⒉ 由whether,if引导的宾语从句

① 由whether（if）引导的宾语从句，实际上是一般疑问句演变而来的。意思是"是否"。宾语从句要用陈述句语序。一般说来，在宾语从句中whether与if可以互换使用，但在特殊情况下if与whether是不能互换的。

如：I wonder whether(if）they will come to our party.

② 只能用whether，不能用if引导的宾语从句

⑴ 在带to的不定式前

如：We decided whether to walk there.

⑵ 在介词的后面

如：I'm thinking of whether we should go to see the film.

⑶ 在动词后面的宾语从句时

如：We discussed whether we had a sports meeting next week

⑷ 直接与or not连用时

如：I can't say whether or not thet can come on time.

③ 只能用if不能用whether引导的宾语从句

⑴ if引导条件状语从句，意为"如果"

如：The students will go on a picnic if it is sunny.

⑵ if引导否定概念的宾语从句时

如：He asked if I didn't come to school yesterday.

⑶ 引导状语从句even if（即使）和as if（好象）时

如：He talks as if he has known all about it.

⒊ 连接代词和连接副词引导的宾语从句

这样的宾语从句实际上是由特殊疑问句变化而来的，宾语从句要用陈述句语序。用于这种结构的动词常常是：see,say,tell,ask,answer,know,decide,show,find out,imagine,suggest,doubt,wonder,discover,understand,inform,advise等。

英语中的连接代词有：who,whom,whose,which,what,在句中担任主语、宾语、定语或者表语。

如：Can you tell me whom you are waiting for?

英语中的连接副词有：when,where,why,how，在句中担任状语的成分。

如：None of us knows where these new parts can be bought.

宾语从句的语序

宾语从句的语序是陈述句语序即：连接代词/副词+主语+谓语+其他成分。

如：I don't know what they are looking for.

Could you tell me when the train will leave?