高考英语whether和if的区别ppt课件.pptx

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1、whetherwhether和if if在名词性从句中的用法区别whether和if均可用在名词性从句当中，但再用法上又有很大的区别。我们将从以下5点来区别二者的用法1.whether1.whether和if if均可用来引导主语从句，但if if引导的从句不能位于句首eg.Whethertheywinorloseisallthesametome.他们是赢是输於我都一样.（此时whether不能换作if）Itsdoubtfulwhethertherellbeanyseatsleft.说不上还有没有空座位了.(此句whether能换作if)语法公式：whether主语从句+谓语+.2用wheth

2、er或if引导的宾语句whether和if均可引导动词后的宾语从句，常可互换。如：Idontknowwhether/ifIwillbeabletocome.我不知道我是否能来.Sheaskedmewhether/ifIwasinterestedinworkingforher.她问我是否有兴趣为她工作。.当whether和ornot连用时，只用whether不用if。当ornot放在whether引导的从句句尾，则可以用if来替换。如:Idontknowwhetherornothewillcome.我不知道他是不是回来。Illbehappywhether/ifIgetthejobornot我能不

3、能得到那份工作都一样高兴语法公式：whether+or not whether/if+or notEverything depends on whether we have enough money.I dont care about whether you have money or not.介词后的宾语从句一般不用if引导，要用whether。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Were worried about _ he is safe.whether语法公式：介词介词

4、+whether宾语从句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我问他这些工作都是他自己做的还是别人帮他做的人帮他做的.在两个供选择的宾语从句之间若在两个供选择的宾语从句之间若用用or,则须重复使用则须重复使用whether语法公式：whether从句+or+whether从句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 su

5、re.我很难说我们是否有时间跟你们一起去语法公式：Whether宾从+主语+谓语.当当whether和和or 连用表示明确的选择时，连用表示明确的选择时，只用只用whether不用不用if。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。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他开车去还是坐火车去,犹豫不决犹豫不决语法公式：whetheror.动词

6、discuss，decide,consider等后习惯上也常用Whether引导从句，不用if。Theydiscussedwhethertheyshouldleaveatonce.他们讨论了是否应该马上离开。Wediscussedwhetherthehouseshouldbesold.我们讨论了这房子是否应卖掉。语法公式：discuss/decide/consider+whether宾语从句Atthemeeting,wediscussed_weshouldemploymoreworkers.A.ifB.whetherC.thatD.不填B.doubt用于肯定结构时，后面用whether/if

7、引导名词性从句；用于否定结构或疑问结构时，后面用 that 引导名词性从句。主语语+doubt+whether/if 从句从句I doubt if he can come back.I dont doubt that从句从句 I dont doubt that he we will win in the sports meetingI doubt _ he will come here on time.A.thatB.whetherC.whenD.whereBbesure用于用于肯定句或疑问句肯定句或疑问句时，后时，后接接that引导的名词性从句；用于引导的名词性从句；用于否否定句时，后接定句

8、时，后接whether/if引导引导的名词的名词性从句。性从句。They are sure that he can help themWe were not sure whether we could win that competition or notat that time Noonewassure_hewouldbeaskedtospeaknextyear.A.whenB.whetherC.whatD.howB3.表语从句用表语从句用whether引导不用引导不用if.The doubt was whether you had broken the beautiful vase.疑问是

9、你是否打坏了这只漂亮的花瓶。疑问是你是否打坏了这只漂亮的花瓶。语法公式：系动词+whether表语从句4.同位语从句用同位语从句用whether引导不用引导不用if.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。是否要另建一幢教学楼的问题还未决定。语法公式：抽象名词+whether同位语从句5.在动词不定式之前，只能用在动词不定式之前，只能用whether，不能用不能用if。The question is whether to go to Munich

10、or Vienna.问题是去慕尼黑还是去维也纳问题是去慕尼黑还是去维也纳.She doesnt knows whether to get married now or wait.是否现在结婚或是等待她不知道。是否现在结婚或是等待她不知道。We were wondering whether to go today or tomorrow.我们弄不清是今天走还是明天走我们弄不清是今天走还是明天走.Im not sure whether to resign or stay on.我拿不准主意是辞职还是留任我拿不准主意是辞职还是留任.语法公式：whether to do Sum up Sum up:whetherwhether与与if if的辨用的辨用表“是否”时，在在名词性从句中下列情况下只用whether。a.主语从句主语从句whether主语从句+谓语+.b.表语从句表语从句系动词+whether表语从句c.同位语同位语从句从句抽象名词+whether同位语从句e.介词后的宾语介词后的宾语从句从句介词介词+whether宾语从句f.后接动词不定式后接动词不定式 (whether to do sth.)g.whether+or not h.whether/if+or not