条件状语从句ppt课件.pptx

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1、,条件状语从句,if (如果)， unless (如果不), so /as long as(只要), once (一旦), in case (万一),条件状语从句常用连词：,引导条件状语从句最常用的连词是if, 由if引导的条件状语从句表示在某种条件下某事很可能发生。如:If you ask him, he will help you. 如果你请他帮忙, 他会帮你的。 If you fail in the exam, you will let him down.,If 引导的条件状语从句(1),当主句为将来时态或具有将来意时，条件状语从句通常要用一般现在时表示将来意义，而不能直接使用将来时态：

2、Ill stay at home if it rains tomorrow. 要是明天下雨，我就呆在家里。【注】有时也可见到 if you will 这样的说法，但那不是将来时态，而是表示意愿或委婉的请求(此处的 will是情态动词)：If you will wait for a moment, Ill go and tell the manager that you are here. 请等一下，我去告诉经理说你来了。,If 引导的条件状语从句( 2),条件状语从句中一般不使用将来时态，尽管主句使用将来时态，而从句用一般现在时或现在完成时。I will come to see you if

3、I have time.我有时间，我就来看你。If the rain stops,I shall go out for a walk.如果雨停了，我就出去散步。If you know the answer ,please raise your hand.Dont play games unless you has finish your homework .Unless you put on a coat ,you may catch a cold.,学习条件状语从句应注意以下几点：（一）,(2) if 从句+祈使句If you want to go ,please let me know.I

4、f the green light isnt on ,wait for a minute.(3) 祈使句+and/or +陈述句。相当于if的状语从句。Study hard and you will pass the exam.=if you study hard ,you will pass the exam.Hurry up ,or you will be late .=if you dont hurry up, you will be late .Work hard , _ you may catch up with your classmates. A. or B.but C. and

5、 D. yet,学习条件状语从句应注意以下几点：(二）,C,(4) 注意条件状语从句是经常发生和一般将会发生的情景和事件，则主句多用一般现在时态。【例】if bears are in danger ,they attack people.如果熊处于危险之中，它们就会对人进行攻击。,学习条件状语从句应注意以下几点：(三）,（5) 条件状语从句中的省略。 Come tomorrow if (it is ) possible. 可能的话，明天来。 I will buy a DVD set if ( it is ) necessary.,学习条件状语从句应注意以下几点：(四）,If（如果） 引导的条件

6、状语从句和if (是否)连接的宾语从句的区别：If you use your head ,youll find a way.如果你动动脑子，你就会想出办法的。I wonder if he has finished his work.我想知道他是否完成他的工作了。,学习条件状语从句应注意以下几点：(五）,10,（ ）1. I dont know if _ tomorrow. A. it doesnt rain B. the rain will stops C. the rains wont stop D. it wont rain （ ）2 . The volleyball match will

7、 be put off if it _ . A. will rain B. rains C. rained D. is raining,练习（1）,D,B,（ ）3. Difficulties are nothing if we _ not afraid of them A. will B. shall C. are D. do,练习（2）,C,C,（ ）4. I dont like to be interrupted if I _ .A. speak B. will speak C. am speaking D. spoke,B,（ ）5. If you _ the book you wil

8、l understand the story better. A. will be reading B. have read C. will have read D. read,（ ）6. Ill go to meet you，if I _ free then. A. would be B. will be C. am D. was,练习（3）,C,B,（ ）7. If you to the music, buy a CD. A. will listen B. listen C. listening D. listened,练习（4）,( ) 9. Be careful, if you _ w

9、ant to make mistakes. A. wont B. dont C. didnt D. not,( ) 10. If he _ , I _ go swimming alone. A. doesnt come will go B. wont come; will go C. will come; wont go D. is coming; dont go,( ) 8. Work hard if you _ to get a good mark. A. wanted B. wanting C. want D. will want,C,B,A,练习（5）,1If she _ (finis

10、h ) work early ,she _(go) home.2If the weather_（be）fine，we_(go)for a walk .3. If I_(have) time tonight ,I _(finish) the book Im reading.,练习（6）,4. If I _(rain) next weekend , we_(not be able to ) plant the vegetable .5. If it_(rain),we_(stay) at home .6.If she_(arrive) ,she _(phone) me .,练习（7）,7. If

11、he_(call),tell him Ill ring back . 8.I dont know if it_(rain)tomorrow .If it _(rain) , we _(not go )to school .,感谢您的聆听！,if从句还表示不可实现的条件或根本不可能存在的条件, 也就是一种虚拟的条件或假设, 从句多用一般过去时或过去完成时。如:If I were you, I would invite him to the party. I would have arrived much earlier if I had not been caught in the traffi

12、c. 如果没有堵车, 我会到的早一点儿。,If 引导的虚拟条件句(3),1.unless conj. 除非, 若不, 除非在的时候You will fail to arrive there in time unless you start earlier. 如果你不早点动身, 你就不能及时赶到那儿。 Unless it rains, the game will be played. 除非下雨, 比赛将照常进行。,Unless引导的条件状语从句,as/so long as 只要As long as you promise to come, Ill wait for you until you c

13、ome. 只要你答应, 我就等你来。So long as youre happy,it doesnt matter what you do.只要你高兴，你做什么都没有关系。You may borrow my book as long as you keep it clean.只要你保持书的清洁，你就可以把我的书借去。Take your umbrella in case it rains.带着你的伞吧，以防下雨。,as/so long as引导的条件状语从句,当主句为将来时态或具有将来意时，条件状语从句通常要用一般现在时表示将来意义，而不能直接使用将来时态：Ill stay at home if

14、 it rains tomorrow. 要是明天下雨，我就呆在家里。【注】有时也可见到 if you will 这样的说法，但那不是将来时态，而是表示意愿或委婉的请求(此处的 will是情态动词)：If you will wait for a moment, Ill go and tell the manager that you are here. 请等一下，我去告诉经理说你来了。,条件状语从句的时态,【注】除以上基本的引导条件状语从句的从属连词外，还有的动词尤其是其分词形式(如suppose, supposing, provided, providing等)和介词短语(如in case,

15、on condition that等)也可用作连词表示条件：In case I forget, please remind me about it. 万一我忘记，请提醒我一下。I will come on condition (that) she is invited too. 如果邀请她来, 那我就来。He may go with us provided providing he arrives in time. 他若及时到，就可以和我们一起走。Suppose 和supposing 引导条件状语从句时，通常用于主句为疑问句的场合：Suppose the boss saw you，what w

16、ould he say? 如果老板看到你，他会怎样说?Supposing he does not come, shall we go without him? 他若不来，是不是不带他去?,条件状语从句的其他形式,条件状语从句中一般不使用将来时态，尽管主句使用将来时态，而从句用一般现在时或现在完成时。I will come to see you if I have time.我有时间，我就来看你。If the rain stops,I shall go out for a walk.如果雨停了，我就出去散步。Dont play games unless you has finish your h

17、omework .If you know the answer ,please raise your hand.Unless you put on a coat ,you may catch a cold.注意条件状语从句是经常发生和一般将会发生的情景和事件，则主句多用一般现在时态。【例】if bears are in danger ,they attack people.如果熊处于危险之中，它们就会对人进行攻击。条件状语从句中的省略。【例】Come tomorrow if (it is ) possible. 可能的话，明天来。I will buy a DVD set if ( it is ) necessary.,学习条件状语从句应注意以下几点：,