1、if條件狀語從句及其時(shí)態(tài)的用法,英國前首相撒切爾夫人（Margaret Thatcher）曾用if條件句對男人和女人進(jìn)行評價(jià)： In politics, if you want someone to make a speech, ask a man; if you want something done, ask a woman.,一、概念,連詞if的意思是“如果”，它引導(dǎo)的句子表示某事發(fā)生所需要的條件，即“在條件下某事才能發(fā)生”，在句子中充當(dāng)狀語，因此我們稱之為條件狀語從句。在復(fù)合句中連詞if引導(dǎo)的句子為從句，被修飾的句子為主句。從句可以放在主句后，也可以放在主句前，從句放在主句前時(shí)，應(yīng)用逗

2、號將它與主句隔開。例如： Well go to the Great Wall if it doesnt rain tomorrow. = If it doesnt rain tomorrow, well go to the Great Wall.,二、用法,1. 條件狀語從句通常由連詞if引導(dǎo)，意為“如果，假如”，主句不能用be going to 表示將來，而應(yīng)該用shall或will。例如： If Im free tomorrow, Ill go with you. 2. if引導(dǎo)的條件狀語從句，主句用一般將來時(shí)，從句則用一般現(xiàn)在時(shí)，即“主將從現(xiàn)”。例如： If it is sunny to

3、morrow, Ill climb the hill.,3. 正確區(qū)分if引導(dǎo)的條件狀語從句和if引導(dǎo)的賓語從句：在條件狀語從句中，if表示“如果”；而在賓語從句中，if表示“是否”?？梢杂孟旅娴姆椒▍^(qū)分： 1) 從句前置法：if引導(dǎo)的條件狀語從句，可以放在主句之前并用逗號隔開，也可放在主句之后；而if引導(dǎo)的賓語從句只能放在主句之后。因此如果把if放在主句之前，句子通順，意義不變，則是條件從句，否則是賓語從句。例如： He will help you if you ask him. = If you ask him, he will help you.,2) whether替換法：if引導(dǎo)賓語

4、從句時(shí)，其意為“是否”，通?？捎脀hether替換，意義不變，而if引導(dǎo)條件狀語從句時(shí)不能用whether替換。因此，可用whether替換的是賓語從句，不能替換的是條件從句。例如： I want to know if you will go tomorrow. = I want to know whether you will go tomorrow. 注意：區(qū)分if的用法有著極為重要的意義，因?yàn)樵跅l件狀語從句中，主句用將來時(shí)，從句用一般現(xiàn)在時(shí)；而在賓語從句中，當(dāng)主句是一般現(xiàn)在時(shí)，從句可用所需的任何時(shí)態(tài)，主句是一般過去時(shí)，從句用過去的某種時(shí)態(tài)。,鞏固練習(xí),一、單項(xiàng)選擇 1. If you _

5、 to the party, youll have a great time. A. will go B. went C. go D. going 2. I _ her the answer if she _ me. A. can tell, will ask B. will tell, will ask C. would tell, ask D. will tell, asks 3. What are you going to do tomorrow? Well go to the library tomorrow if it _. A. isnt rain B. rain C. wont

6、rain D. doesnt rain 4. Do you know when he will come back tomorrow? Sorry, I dont know. When he _ back, Ill tell you. A. comes B. will come C. come D. may come,5. Ill give the book to him if he _ here next Sunday. A. will come B. comes C. is coming D. came 6. There _ an English film in our school to

7、morrow. A. is going to have B. will have C. is going to be D. has 7. Ill wake you up when he _back. A. will B. is going to come C. comes D. come 8. The football match will be put off if it _. A. will rain B. rains C. rained D. is rained 9. There _ a basketball game this afternoon. A. is going to hav

8、e B. will be C. is going to play D. will play 10. I wont go if it _ tomorrow. A. rain B. is raining C. rains D. will rain,二、用所給詞的適當(dāng)形式填空 1. If you _ (feel) tired, you _ (have) to have a rest. 2. Where _ he _ (see) the film if he _ (have) time? 3. If there _ (be) fewer trees, there _ (be) more polluti

9、on. 4. He _ (dress) more casually if he _ (not work) on weekends. 5. If Marcia _ (live) alone, she _ (keep) a pet parrot. 6. Lana _ (buy) a new dress if the old one _ (be) out of style. 7. The twins _ (fight) if they _ (argue).,8. I _ (have) a bake sale if I _ (need) money for education. 9. Peter _

10、(send) me a beautiful souvenir if he _ (go) to Spain. 10. If Mr. Green _ (say) I am hard- working, my parents _ (feel) glad. 11. I _ (go) to the beach if it _ (not rain) this week. 12. _they _ (have) a match if the P.E. teacher_ (be) not busy? 13. He _ (write) a letter to his grandparents if he _ (g

11、et) his report card this week. 14. If she _ (get) up late, she _ (not catch) the early bus. 15. Peter _ (major) in English if he _ (pass) the exams in Peking University.,三、完成句子 1.如果他遲到了，會發(fā)生什么事情？ What _ _ if he _ late? 2. 如果努力學(xué)習(xí)，你就會取得好成績。 If you_ _, you _ _ good _. 3. 他如果看電視太久了，他的父母會不高興。 If he _ TV too much, his parents _ _ unhappy. 4. 如果我們?yōu)樗e辦生日聚會，大家都會來的。 Everyone _ _ if we _a birthday party _ him.,5. 如果明天不下雨，我會和你一起去公園的。 If it _ _ tomorrow, I _ go to the park _ you. 6. 如果她睡過頭了，就會誤了開會的。 She _ _ _ _ the meeting if she _ _. 7. 如果他有空，他會幫助你的。 If he _ _, he _ _ you.