这是宾语从句，关于宾语从句的基本用法，这里很详细
http://zhidao.baidu.com/question/80556544.html?si=2&wtp=wk另外应注意
宾语从句从句的语序必须是陈述语序，即连接词+主语+谓语+其他成分
例：I believe that they will come soon.
He asked me whether I was a teacher.
They wanted to know what they can do for us.
带有宾语从句的复合句的构成
带有宾语从句的复合句就是用连接词把一个主句和一个宾语从句连接在一起。连接词有：that(可省略)，what, who, when, where, why, which, if, whether, how.
1 He suggested (that) we should clean the corridor every day.
宾语
2 He told me (that) he would leave Dalian airport at 8pm.
间接宾语 直接宾语
3 He told me where he was going to travel that summer.
间接宾语 直接宾语
4 He wanted to know what the manager had said at the meeting.
who hadn’t passed the exam.
when she would leave this building.
why she cried last night.
where she was going to study.
which student was his partner in the short play.
if (whether) Tom could play basketball with him that morning. how she managed to solve the problem.
why water flows from a high position to a lower position.
在例子4中，当主句是过去时态时（一般过去时，过去进行时，过去将来时，过去完成时），从句根据不同情况必须使用过去时态的一种，（大自然的现象和真理除外）。
5 He is wanting to know what I can cook for dinner.
who broke the window yesterday.
when I can have a holiday.
why I failed the exam yesterday.
where I should have dinner with my friend tonight.
which book is the best one.
if (whether) I have passed the exam.
how my cat escaped from the room last night.
在例子5中，当主语是现在时态时（一般现在时，现在进行时，一般将来时，现在完成时），从句可根据不同情况使用各种时态。
三、注意
A 宾语从句必须用陈述语序。
False: He is wondering when can he finish this difficult job. Right: He is wondering when he can finish this difficult job.
B 有时候可以用it 作形式宾语，而把真正的宾语从句放在后面。 Bad: I thought that he could finish this job in just two hours impossible.
Good: I thought it impossible that he could finish this job in just two hours.
Bad: He left whether we should continue this project to my judgment.
Good: He left it to my judgment whether we should continue this project.
C 带有宾语从句的复合句的否定形式一般是否定主句。 Bad: I think he doesn’t like the English teacher. Good: I don’t think he likes the English teacher.
D 主句一般过去时态，从句也要用过去时态；具体细节请看第一部分。 False: He wanted to know why he is crying in the corner.
Right: He wanted to know why he was crying in the corner.