连词：that (that 常可省略),whether, if
代词：who, whose, what ,which
副词：when ,where, how, why 等。
say, think, insist, wish, hope, demand, imagine, wonder, know, suppose, see, believe, agree, admit, deny, expect, explain,
order, command, feel, dream, suggest, hear, mean, notice, prefer, request, require, propose, declare, report等。
例句：The boy believes that he will travel through space to other planets.
当主句谓语动词是 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。
例句：I don’t think it is right for him to treat you like that.
例句：He said (that) you were too young to understand the matter and that he was asked not to tell you.
例句：Just then I noticed, for the first time, that our master was wearing his fine green coat and his black silk cap.
例句：I can’t tell him that his mother died.
例句：I find it necessary that we should do the homework on time.
例句：I wonder whether(if) they will come to our party.
例句：We decided whether to walk there.
例句：I’m thinking of whether we should go to see the film.
例句：We discussed whether we had a sports meeting next week
例句：I can’t say whether or not thet can come on time.
例句：The students will go on a picnic if it is sunny.
例句：He asked if I didn’t come to school yesterday.
引导状语从句even if（即使）和as if（好象）时
例句：He talks as if he has known all about it.
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。
例句：Can you tell me whom you are waiting for?
例句：None of us knows where these new parts can be bought.