条件状语从句.ppt

1、条件状语从句,预习： 1. 什么是条件状语从句？ 2. 条件状语从句如何与主句时态搭配？,条件状语从句 经典例句： 1. If you stick a pin into a balloon, it bursts. 2. Unless you keep ice cream in a fridge, it melts.,一、什么是条件状语从句？ 在某种条件下，可能发生某事。而由if/unless引导的表示条件的句子，就叫条件状语从句。 eg: If you get up early, you will catch the bus. If you put wood into water, it fl

2、oats.,二、时态 1当主句和从句所表示的是原理、客观真理、规则时，主句是一般现在时（包括祈使句和含有情态动词can/may/must等），从句也要用一般现在时。 例如： 1) If you put a piece of paper into water, it gets wet如果你把一张纸放进水中，它会变湿。(原理),2)Be careful if you cross the road.(祈使句) 3) You must see the doctor if you are ill.( 含有情态动词）,2. 在if条件状语从句中，如果从句谈论的是一个可能发生的事实及其产生的相关结果，主句用

3、一般将来时，从句用一般现在时。 eg: 1) If it rains tomorrow, we will not go to the zoo. 2) If you go to bed earlier, you wont feel tired in the morning.,3. 如果从句用现在进行时或现在完成时，主句需用一般将来时。 1） If you are looking for Peter youll find him upstairs. 如果你是在找彼得，上楼就会找到他。 2） If you have finished dinner Ill ask the waiter for the

4、 bill. 如果你吃完了，我就叫服务生来算账。,三、条件状语在句中的位置 大多数情况下，if/unless从句既可以放在主句之前也可以放在主句之后。当从句置于主句之前时，常用逗号与主句隔开。 It floats if you put wood into water.=If you put wood into water, it floats.,四、转换 1、当主语是you时,if引导的条件状语从句可与“祈使句+ andor+简单句”进行句型转换。and表示句意顺承；or表示转折，意为“否则”。 例如： Take care, or youll fall off the tree. 小心，否则你

5、会从树上掉下来。 =If you dont take care, youll fall off the tree.,2. unless也可引导条件状语从句，相当于if.not，意思是“如果不、除非”。 例如： You will fail in Math unless you work harder. = You will fail in Math if you dont work harder. 你要是不再加把劲儿，数学考试就不及格了。,五、拓展 1. if从句还可以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，主句则用虚拟语气。 1)

6、If I were you, I would invite him to the party. 2) I would have arrived much earlier if I had not been caught in the traffic.,2. if表示“是否”时引导宾语从句，意思同whether. I dont know if he can come. If he comes, I ll tell you at once.,一、用括号内单词的适当形式填空 1.If you _(feel) tired, you _ (have) to have a rest. 2. Where _

7、 he _(see) the film if he _(have) time? 3. If there _(be) fewer trees, there _( be) more pollution. 4. He _(dress) more casually if he _( not work) on weekends. 5. If Marcia _(live) alone, she _( keep) a pet parrot.,6. If you _(need) the instructions in English, go to our website. 7. If the green li

8、ght_(not be) on, we must wait for one minute. 8. I dont know if he_(come) tomorrow. 9. If you dont put fish back to water, it_(die). 10. Dont go out tomorrow if it _(rain).,二、同义句转换 1. Play some sports, and youll be healthy. _ _ play some sports, youll be healthy. 2. If you study hard, you will catch

9、 up with your classmates. _ you study hard, you wont catch up with your classmates. 3.Fish will die without water. Fish will die _ there is no water.,4.Dont stay up later,or wont be sleepy tomorrow. _ you _ stay up late,you wont be sleepy tomorrow. 5.I will come to see you unless I am too busy. _ I

10、am _ too busy, I will come to see you.,三 根据汉语提示完成句子,1.如果我有时间的话，我就会去帮你。 If I _ _,I _ _ you with it. 2.如果明天不下雨，我们就去徒步旅行。 If it _ _ tomorrow,well go hiking. 3.我们没有人能赶上汤姆，除非他不跑。 None of us can _ _ _ Tom _ he doest run.,4.他不会迟到的，除非他生病。 He _ _ late _ he _ ill. 5.如果你看见汤姆，叫他来我办公室。 _ Tom to come to my office

11、 _ you _ him.,Good morning, ladies and gentlemen! May I have your attention,please? Im a volunteer and Im glad to tell you something about protecting the beaches in Shenzhen. As we know, beaches are great places for us to travel and relax. In order to protect the beaches, our government has made som

12、e strict rules. However, some citizens dont understand it.,In my opinion, these strict rules can help us create a better beach environment. The beaches will be cleaner and more beautiful if each tourist can realize the imoportance of protecting them.,So I hope all of us will try to follow these: Never throw rubbish everywhere. Dont step on the grass or pick flowers near the beach.