1.whether和if均可用来引导主语从句,但if引导的从句不能位于句首。
如: Whether they win or lose is all the same to me.  他们是赢是输於我都一样.(此时whether不能换作if )
    It's doubtful whether there'll be any seats left.    说不上还有没有空座位了. (此句whether能换作if)

2.whether和if均可用来引导宾语从句。
如:I don't know whether/if I will be able to come.我不知道我是否能来.
She asked me whether/if I was interested in working for her.她问我是否有兴趣为她工作。
We'll be told tomorrow whether we should take the exam or not.我们明天才知道是不是应该参加考试.
 桂林山水教案I asked him whether he had done all the work himself or whether he had had any assistance. 我问他这些工作都是他自己做的还是别人帮他做的.
( 注意: 在两个供选择的从句之间若用or字, 则须重复whether一字. )


注:  跨行转账如何收费当强调宾语从句并将其提前时只能用whether。
    如:Whether I'll have time to go with you I am not sure.我很难说我们是否有时间跟你们一起去。
      从句作介词宾语时只用whether不用if。
如:She was undecided about whether she should accept his offer.她拿不定主意应该不应该接受他的好意
      当whether和or not连用时,只用whether不用if。当or not放在whether引导的从句句尾,则可以        用if来替换。
      如: I don’t know whether or not he will come.我不知道他是不是回来。
      I'll be happy whether/if I get the job or not我能不能得到那份工作都一样高兴
      当whether和or 连用表示明确的选择时,只用whether不用if。
      如:He asked me whether I wanted to go there by train or by bus.他问我是想乘火车还是坐公共汽车去那里。
          He hesitated about whether he should drive or take the train.他开车去还是坐火车去,
犹豫不决

注:whether 和or 连用还可以引导让步状语从句,此时也不用if。
    如:We'll go on with the work, whether we can find the necessary tools or not.
不管我们能否到所需的工具,我们要把这件工作做下去。
            Whether or not it rains / Whether it rains or not, we're playing football on Saturday.
              无论下不下雨, 我们星期六一定踢足球.
    ⑸ 动词discuss,decide,consider等后习惯上也常用Whether引导从句,不用if。
        They discussed whether they should leave at once.他们讨论了是否应该马上离开。 
      We discussed whether the house should be sold.  我们讨论了这房子是否应卖掉。   

3.表语从句用whether引导不用if.
如:The doubt was whether you had broken the beautiful vase.      疑问是你是否打坏了这只漂亮的花瓶。

4. 同位语从句用whether引导不用if.
如:The question whether we'll build another lecture building hasn't been settled.
是否要另建一幢教学楼的问题还未决定。
5. 在动词不定式之前,只能用whether,不能用if。
如:The question is whether to go to Munich or Vienna.      问题是去慕尼黑还是去维也纳.
  ②She doesn't knows whether to get married now or wait.  琉璃繁缕是否现在结婚或是等待她不知道。
  ③We were wondering whether to go today or tomorrow.    我们弄不清是今天走还是明天走.
  ④I'm not sure whether to resign or stay on.              我拿不准主意是辞职还是留任.
强化练习:
1. The question has not been answered ____ Taiwan will be included on the Olympic torch relay route.
A.that      B.whether      C.which        D.if
2. You have not yet answered my question _____ I can join in the party tonight or not.   
  A. whether                B. if                              C. that                        D. which
3.— I d like to invite you to a party this evening.
— Thank you, but _____ I’ll be free I m not sure at the moment.
A. while                  B. if                      C. when        D. whether
4.---What are you anxious about?
    ---___________
A.      If we succeed  B.That we can succeed      C. Do we succeed  D.Whether we can succeed
5. Only when _____ the painting _____ decide ______the painting is worth buying.   
A. he sees, he can ,whether    B. does he see, can he,  if 
C. he sees, can he ,whether    D. sees he, he can,that
6. _____ English is his favourite subject
    A. I asked him if    B. I asked him that whether C. I asked him that    D. I asked him which
7. _____ they’ll go to the Summer Palace ____ the weather.
    A. If; depends on    B. Whether; depends upon  C. Whether; depended on    D. If; depended upon
8.It isn’t quite _____ ______ he will be present at the meeting.
黄磊 似水年华    A. sure; whether    B. sure; if      C. certain; whether    D. certain; that
9. _____ the 2008 Olympic will be held in Beijing is not known yet.
    A. Whether    B. If    C. Whenever    D. That
10. No one was sure _____ he would be asked to speak next year.
    A. when    B. whether    C. what    D. how
11. It is still a question to us all _____ there is any living thing in some other places in the space.
    A. whether    B. which      C. what    D. where
whether是什么意思12. I doubt _____ he will come here on time.
A. that    B. whether      C. when    D. where
13.    The point is not who said the words, _____ they are true or not.
A. but whether    B. and whether    C. but how    D. and how 
14. “What did he ask you?” “_____ I would be late.”
A. That    B. When    C. Where    D. Whether
15. He treated all the people around him,______he knew or he didn't know,______.
    A. if, friendly                B. whether, friendly 今年高考分数线公布
    C. if, in a friendly way      D. whether, in a friendly way
16. At the meeting, we discussed _____ we should employ more workers.
    A. if      B. whether    C. that    D.不填 



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