宾语从句是名词性从句的一种。在主从复合句中充当宾语，位于及物动词、介词或复合谓语之后的从句称为宾语从句。宾语从句分为三类：动词的宾语从句，介词的宾语从句和形容词的宾语从句。

1. 宾语从句的连接词

（1）从属连词that, if, whether
需要注意区分的是：that引导表示陈述句的宾语从句，if和whether引导表示“是否”的一般疑问句的宾语从句。例如：
He told me that he would go to the college the next year.
他告诉我他明年上大学。
I don't know if there will be a bus any more.
我不知道是否还会有公交车。
Nobody knew whether he could pass the exam.
没有人知道他是否会通过考试。
（2）连接代词who, whom, whose, what, whoever, whomever, whosever, whatever, whichever
需要注意的是：连接代词一般指疑问,但what, whatever，whichever 除了指疑问外，也可以指陈述。例如：
Do you know who has won Red Alert game?
你知道是谁赢得了红色警戒的游戏么？
The book will show you what the best CEOs should know.
这本书会告诉你最好的执行总裁该了解什么.
Have you determined whichever you should buy, a Galaxy Note 7 or iPhone 7?
你决定好是买三星7还是iPhone 7了吗?

2. 哪些宾语从句不可以省略引导词that

（1）表达人主观意见的动词
add, agree, announce, argue, assume, complain, decide, hold, indicate, insist, intend, learn, promise, point out, remark, suggest, state 等之后的宾语从句的引导词that需保留。例如：
I complained that I had been unfairly treated.
我抱怨说自己受到了不公平的对待。
（2）及物动词+两个及以上宾语从句
及物动词后跟有两个或两个以上的宾语从句时，最后一个从句的that不可省略。例如：
I realize that I'm in charge and that everybody accepts my leadership.
我意识到要对这一切负责，并且每个人都要听从我的领导。
（3）动词+双宾语
当动词后跟有复合宾语结构时，it作形式宾语，that从句作真正宾语，引导词that不可省略。例如：
We consider it an honor that we can have the pleasure of serving you.
为您效劳真是我们的荣幸。
（4）出现插入语
当动词和that从句之间有插入语时，that不可省略。例如：
The secretary said, pleasantly and sternly, that our thinking was too slow to suit the needs of modern society.
书记语重心长地说，我们的思维已落后于现代社会的需求。
（5）状语紧跟that
当that从句的状语紧跟在that之后时，that不可省略。例如：
They told us that once again the situation was serious.
They told us once again that the situation was serious.
他们再次告诉我们情况十分严重。