宾语从句。

① 在及物动词的后面可以接一个名词来充当宾语，如： I knew the man. 而这时也可以用一个句子来充当宾语，如：I knew that he was a good man. 这时宾语从句的连接词有 that, (that 只在从句中起联接作用，不在句中充当语法成分，既不是主语也不是宾语，所以在口语中常常被省略。如：I am sure (that) she has passed the exam.

② if, whether 它们在宾语从句中只起连接作用，不起语法作用，当作是否讲。通常可以互换

例如：I ask him if (whether) he has had his lunch.

有些情况只能用whether：

（1）从句中有 or not 结构时，要用 whether,

例如：I ask him whether he has had his lunch or not.

（2）在带to的不定式前要用whether

例如：We decided whether to walk there.

（3）在介词的后面要用whether

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

只能用if，不能用whether的情况：

（1）意为“如果”时只能用if

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

（2）引导否定概念的句子时只能用if

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

③ what 它在宾语从句中除了作连接词外，还要作主语或宾语成份，如：I don't understand what you said (what 作 said 的宾语)。又如： I asked him what made him sick. (what 在宾语从句中作主语)。

④ who，它也和what一样，在句中除作连接词外，可以充当句中的成份，如：I know who she is looking for?

⑤ whose 如： I want to know whose book this is?

⑥ which 如： Do you know which book is mine?

在连接词中还有4个常用的连接副词：

① how 它的应用最广，如：how much, how many, how long, how soon.

how old …。如：How much does it cost?

②　when 它只是连接时间状语，如：Please tell me when the meeting will begin?

③　where 它连接地点状语，如： Where are you from?

④　why 它要连接的是原因状语从句，如：The teacher asked why Tom didn't come to school.

在考试中常见到的考点是：宾语从句的时态与主句时态的呼应问题。

①　主句谓语动词如果是现在时或将来时，宾语从句的时态可以是任何所需要的时态，如：

I know he didn't come. 我知道他没来。

I know he will come tomorrow. 我知道他明天来。

I know he has gone to London. 我知道他已去伦敦了。

②　主句中的谓语动词若是过去时，宾语从句也要用过去时态中的某一种。比如：一般过去时，过去进行时，过去将来时，过去完成时。除了在表达宇宙中的客观真理时，不能用现在时态。如：

I wanted to know when he would come.

The teacher told me the earth moves around the sun.

＊注意事项：当主句的谓语动词是think， believe ，suppose， expect等词，而宾语从句的意思是否定时，常把否定转移至主句表示。

例如：I don't think it is right for him to treat you like that.