Chapter 1 语法If 和unless 引导的条件状语从句我们用if 引导的条件状语从句来讨论可能的条件以及该条件成立时可能的结果。

一. 学习if 引导的条件状语从句的用法，我们可先从如下的口诀入手：If条件句不一般，几个要点记心间；条件句，放在前，逗号要句中间条件句表可能，主句多用将来时；条件句表事实，主句常用现在时。

We can walk there if we can't find a bus. 如果我们找不到公车，也能走路去那里主句条件状语从句If it rains tomorrow, we will not go to the zoo. 如果明天下雨，我们就不去动物园条件状语从句主句What will you go if you find someone in danger? 主句条件状语从句如果你发现某人有危险，你会怎么做？If 条件句有不同的类型，简述如下：1.用if条件句表达客观真理或普通现象If 条件句用于表达客观真理或普通现象时，主，从句时态均用一般现在时，如：Eg. If you freeze water, it turns into ice.A fish dies if you take it out of water.2.用if 条件句表示将来可能发生的事情在表示将来可能发生的事情的if 条件句中，主句用一般将来时，而if 从句用一般现在时表示将来的时间，即主将从现Eg. If I like the house, I will buy it. 如果我喜欢这房子，我就会把它买下I will tell her if I see her. 如果我见到她，我就会告诉她。

主句中的will 也可以用情态动词can, may 或might 等代替。

如：Eg. If they are friendly，I might invite them to the party. 如果他们很友善，我可能会请他们去参加聚会If we hurry now, we can stop for coffee later. 如果我们现在抓紧时间，就可以稍后去喝咖啡注意：在条件句中，主句部分只能使用动词will 的一般将来时，不能使用be going to 的结构二. Unless 的条件句表示在特定条件下，才决定做或不做一件事，中文用的连接词一般是“除非”和“否则”。

如：除非刮台风，否则演唱会将如期进行。

在英语中，我们可以用unless表达这个意思，相当于if not。

以这个句子为例：The concert will be held as schedule unless there is a typhoon.= the concert will be held as schedule if there is not a typhoonShe will keep on singing unless she is told to stop. 她会一直唱下去，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（否则）来做同义句转换Unless you listen carefully, you won't know the answer.= if you don't listen carefully, you won't know the answer.= you should listen carefully, or you won't know the answer.深圳中考题：1.If I ______ his phone number, I will tell you.A.findB. foundC. will findD. have found2.We will go camping if it _____ tomorrow.A. Won't rainB. didn't rainC. doesn't rainD. isn't raining3.I'm waiting for my friend. If he _____ , I ______ swimming alone.A. doesn't come; will goB. won't come; will goC.will come; won't goD. don't come; will go4.____ you go to the supermarket at 7 p.m, you can buy a lot of cheap food.A. IfB. UnlessC. WhetherD. When5.I won't get to the party on time _____ I catch the first train tomorrow morning.A. IfB. UnlessC. WhetherD. When6. -- S hall we go on a picnic this weekend?---- G ood idea! Unless it ________ .A. rainsB. doesn't rainC. rainD. won't rain7. - Can I change the jacket for another one _____ it doesn't fit me well?---- Of course.A. unlessB. ifC. thatD. though8.Nobody can learn maths well he works hard on it.A ifB unlessC thoughtD however9.If fish away from water, they die.A are taking, won'tB are taken, willC are being taken, willD take, won't10.Each student can ask teachers for help if he how to work out the problem.A will knowB won't knowC don't knowD doesn't know练习:A woman should never be seen eating or drinking, unless it be lobster salad andChampagne, the only true feminine and becoming viands.Lord ByronI don't feel right unless I have a sport to play or at least a way to work up a sweat. HankAaronNo great poetry, of whatever kind, is conceivable unless the subject has become integrated with the poet's mind and mood. Lascelles AbercrombieI'm not going to just say nice things about everybody unless I mean it. F. Murray Abraham Unless you're willing to have a go, fail miserably, and have another go, success won'thappen. Phillip Adams1.If I ___ you, I _____ very happy.A. were, would beB. am, shall beC. were, shall beD. am, would be2.If he had not lost his money, he __ the piano last week.A. would buyB. had boughtC. could have boughtD. bought3. _ I known it, I should have told him.3 / 54. _ the clouds, you would find the airplane in the sky easily.A. Were it not forB. If it had not been forC. If it were notD. Had it not been for5.If I had known that, I ___ so.A. wouldn't doB. won't doC. didn't doD. wouldn't have done6.If it ___ so hard, we'd go to town.A. isn't rainingB. weren't rainingC. doesn't rainD. isn't going to rain1.答案A 2 答案C 3.答案B 4.答案A 5.答案D 6.答案B7.He ____ you if you __ to see him that afternoon.A. might tell, were goingB.told, were goingC.might have told, had goneD.should tell, went8.If you had started sooner, you __ there.A. may have gotB. might have gotC. shall have gotD. must have got9.If we were to be 2oo years old, we _ everything.A. will changeB. can changeC. could changeD. shall change10.I don't think that I shall fail, but if I ___ I would try again.A. failB. would failC. should failD. had failed11.If you __ to see Mary, what would you tell her?A. areB. will be goingC. mustD. were12.If the train leaves at half past ten, there __ no time to lose.4 / 5A. wouldB. isC. willD. has7.答案C 8.答案B 9.答案C 10.答案C 11.答案D 12.答案Bunless…“除非，如果不……”（=if…not）［例句］ wI shall go tomorrow unless it rains. 如果不下雨，我明天去。