if和unless的用法講解

1、if和unless的用法講解Chapter 1 語法 If 和 unless引導的條件狀語從句我們用if引導的條件狀語從句來討論可能的條件以及該條件成立時可能的結果。一. 學習if引導的條件狀語從句的用法，我們可先從如下的口訣入手：If條件句不一般，幾個要點記心間；條件句，放在前，逗號要句中間條件句表可能，主句多用將來時；條件句表事實，主句常用現(xiàn)在時。We can walk there if we cant find a bus. 如果我們找不到公車，也能走路去那里主句 條件狀語從句If it rains tomorrow, we will not go to the zoo. 如果明天下雨，

2、我們就不去動物園條件狀語從句 主句What will you go if you find someone in danger? 主句 條件狀語從句如果你發(fā)現(xiàn)某人有危險，你會怎么做？If 條件句有不同的類型，簡述如下：1. 用if條件句表達客觀真理或普通現(xiàn)象 If條件句用于表達客觀真理或普通現(xiàn)象時，主，從句時態(tài)均用一般現(xiàn)在時，如：Eg. If you freeze water, it turns into ice. A fish dies if you take it out of water. 2. 用if 條件句表示將來可能發(fā)生的事情 在表示將來可能發(fā)生的事情的if條件句中，主句用一般將來

3、時，而if從句用一般現(xiàn)在時表示將來的時間，即主將從現(xiàn) Eg. If I like the house, I will buy it. 如果我喜歡這房子，我就會把它買下 I will tell her if I see her. 如果我見到她，我就會告訴她。主句中的will也可以用情態(tài)動詞can, may 或might等代替。如：Eg. If they are friendly，I might invite them to the party. 如果他們很友善，我可能會請他們?nèi)⒓泳蹠蘒f we hurry now, we can stop for coffee later. 如果我們現(xiàn)在抓緊時

4、間，就可以稍后去喝咖啡注意：在條件句中，主句部分只能使用動詞will的一般將來時，不能使用be going to的結構二. Unless 的條件句表示在特定條件下，才決定做或不做一件事，中文用的連接詞一般是“除非”和“否則”。如：除非刮臺風，否則演唱會將如期進行。在英語中，我們可以用unless表達這個意思，相當于if not。以這個句子為例：The concert will be held as schedule unless there is a typhoon.= the concert will be held as schedule if there is not a typhoon

5、She will keep on singing unless she is told to stop. 她會一直唱下去，除非有人叫她停止= she will keep on singing if she is not told to stop也可以用or(否則) 來做同義句轉(zhuǎn)換Unless you listen carefully, you wont know the answer. = if you dont listen carefully, you wont know the answer.= you should listen carefully, or you wont know

6、the answer.深圳中考題：1. If I _ his phone number, I will tell you.A. find B. found C. will find D. have found2. We will go camping if it _ tomorrow.A. Wont rain B. didnt rain C. doesnt rain D. isnt raining3. Im waiting for my friend. If he _, I _ swimming alone.A. doesnt come; will go B. wont come; will

7、go C.will come; wont go D. dont come; will go4. _ you go to the supermarket at 7 p.m, you can buy a lot of cheap food.A. If B. Unless C. Whether D. When5. I wont get to the party on time _ I catch the first train tomorrow morning.A. If B. Unless C. Whether D. When6. -Shall we go on a picnic this wee

8、kend? -Good idea! Unless it _.A. rains B. doesnt rain C. rain D. wont rain7. -Can I change the jacket for another one _ it doesnt fit me well? - Of course.A. unless B. if C. that D. though8. Nobody can learn maths well he works hard on it.A if B unless C thought D however9. If fish away from water, they die.A are taking, wont B are taken, will C are being taken, will D take, wont10. Each st