宾语从句引导词

如果从句是陈述句，引导词用that（that在口语或非正式文体中常省略）；如果从句是一般疑问句，引导词用if/whether；如果从句是特殊疑问句，引导词用由疑问词转换而来的疑问代词/副词。
 
一) 以that 引导的宾语从句，主要用来引导陈述句形式的宾语从句，that可以省略。
I know (that) he is a Canadian athlete.
Do you think (that) the children need to write a song?
Maria says (that) she doesn’t like the uniforms.
She told me (that) she would like to go with us.
 
二) 以whether 或 if 引导的宾语从句，主要用来引导一般疑问句意思或选择疑问句意思的宾语从句。
whether和if都可以引导宾语从句，表示“是否”，在口语或间接引语中两者可以互换使用。如：
I wonder if / whether I can get some advice from you.
Ask him whether / if he can come.
 
但在有些情况下，只能用whether，不能用if：
1. whether引导的从句常可以与连词or或or not直接连用，而if一般不能。如：
正： Let me know whether you can come or not.
误： Let me know if you can come or not.
2. 当宾语从句提到句首时，只能用whether引导，而不能用if。如：
正： Whether it is true or not, I can’t tell.
误： If it is true or not, I can’t tell.
3. whether可以引导带to的不定式，if则不能。如：
正： I don’t know whether to accept or refuse.
误： I don’t know if to accept or refuse.
4. whether及其引导的成分可放于介词之后，作介词的宾语，但if不能。如：
正： I worry about whether I hurt her feelings.
误： I worry about if I hurt her feelings.
5. whether可以引导从句，作主语、表语或同位语，而if不能。如：
正： It was uncertain whether he would come.
误： It was uncertain if he would come.
6.若用if会引起歧义时，则用whether。
Please let me know if you like the book．可理解为：
a．Please let me know whether you like the book.
b．If you like the book，please let me know.
 
三) 疑问词引导的宾语从句
疑问代词：what、whom、 who、whose、which
疑问副词：when、where、why、how
例句：1、The book will show you what you must do .
      2、I want to know who made the toy.
      3、Please tell me whose book this is.
      4、I  wonder  whom  you  like.
      5、Please tell me where you are from.

(责任编辑：谷雨英语单词速记网)