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1、由whether,if 引导的宾语从句（一）由whether,if 引导的宾语从句由whether(if)引导的宾语从句，实际上是一般疑问句演变而来的。意思是“是否”。宾语从句要用陈述句语序。一般说来，在宾语从句中whether与if可以互换使用，但在特殊情况下if与whether是不能互换的。例句：I dont know whether(if) they will come to our party.（二）只能用whether，不能用if引导的宾语从句1. 在带to的不定式前：We have to decide whether to walk there. 我们得决定是否要走路去那里。2.
2、在介词的后面：Im thinking about whether we should go to see the film.3. 直接与or not连用时例句：I cant say whether or not they can come on time.=I cant say whether they can come on time or not.我没法说清楚他们是否会按时来。4. 当强调宾语从句并将其提前时,只能用whether。 如:Whether Ill 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。5. 当whet
3、her和or 连用表示明确的选择时。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。6. 动词discuss，decide,consider，sure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 were not sure whether the house should be sold(or not). 我们不确定这房子是否应卖掉。（三）其他只
4、能用whether不能用if的情况1.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。2 同位语从句用whether引导不用if. 如: The question whether well build another lecture building hasnt been settled. 是否要另建一幢教学楼的问题还未决定。3位于句首的主语从句 只能用.whether。如： Whether they win or lose is all the sa
5、me to me. 他们是赢是输於我都一样.（此时whether不能换作if ） Its doubtful whether therell be any seats left. 说不上还有没有空座位了. (此句whether能换作if) 只能用if不能用whether引导的宾语从句1. if引导条件状语从句，意为“如果”例句：The students will go on a picnic if it is sunny tomorrow.如果明天天晴学生们就会去野餐。2. 宾语从句是否定句时，用if例句：He asked if I didnt come to school yesterday.
6、他问我昨天是否没到学校去。3. 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.强化练习： B 1，We will go swimming _it is fine tomorrow A. while B. if C. when D. whetherA 2. You have not yet answered my question _ I can join in the party tonight or not. A. whether B. ifC. thatD. whichD 3 I d like
7、 to invite you to a party this evening. Thank you, but _ Ill be free I m not sure at the moment. A. while B. if C. when D. whether D 4-What are you anxious about? -_A. If we succeed B.That we can succeed C. Do we succeed D.Whether we can succeedC 5. Only when _ the painting _ decide _the painting is
8、 worth buying. A. he sees, he can ,whether B. does he see, can he, ifC. he sees, can he ,whether D. sees he, he can,thatA 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 whichB 7. _ theyll go to the Summer Palace _ the weather. A
9、. If; depends on B. Whether; depends upon C. Whether; depended on D. If; depended uponC 8.It isnt quite _ _ he will be present at the meeting. （it is 。that 结构中只能有certain不能用sure） A. sure; whether B. sure; if C. certain; whether D. certain; that B 9He asked me _I hadnt finished my homework他问我是否没有完成作业。 A. while B. if C. when D. whether B 10. No one was sure _ he would be asked to speak next year. A. when B. whether C. what D. howB 11. I doubt(怀疑) _ he will come here on time.A. that B. whether C. when D. where