语法课条件句Conditional.ppt

条件句 Conditional,条件句的结构：条件状语分句+主句,第一种类型：真实条件句 Real Conditional,1.表示普遍真理和客观事实 Eg: If you heat ice, it melts. If you pour oil on water, it floats. 由上述诸例可以看出，凡表示不受时间限制的自然法则的条件句，其从句和主句的谓语动词都用一般现在时： (If) simple present +(Main) simple present 2.表示现在习惯的动作 Eg: If I make a promise, I keep it. If it rains, I go to work by car. 在上述表示现在习惯动作的条件句中，从句和主句的谓语动词也都是用一般现在时： (If) simple present +(Main) simple present 3.表示过去习惯动作 Eg: If I was hungry, I usually had a full meal. If I made a promise, I kept it. 在上述表示过去习惯动作的条件句中，从句和主句的谓语动词都用一般过去时： (If) simple past +(Main) simple past,第二种类型：真实条件语句的主体,这种句式可分为:“基本形式” (Basic Form)，“变体形式”(Variant Form)和“替换形式”(Alternative Form) 1.基本形式(Basic Form) Eg: If it is fine tomorrow, we can have a picnic somewhere. If you wake up before me, give me a call. 从上述诸例可以看出，这一类型条件语句有两个基本形式： 一是从句用一般现在时表示将来时间，主语用shall / will / can / may 等+不定式： (If) simple present + (Main) shall / will ,etc + inf 二是从句用一般现在时表示将来时间，主句用动词祈使式： (If) simple present + (Main) imperative,2.变体形式(Variant Form) 这种形式又有三种分类 从句动词不管主语的人称和数如何，一律用 should + 不定式，主句动词可根据语义意图采用不同形式。 Eg: If it should rain again, the flowers will bloom. If I should be detained, start the program without me. 在这里，should 仅表示一种不太肯定的婉转口气，并不影响条件的真实性。 在if-分句中用“will + 不定式”并不单纯表示将来意义，这里的 will 是个表示“意愿”的情态助动词，相当于 be willing to Eg: If you will reserve seats, we shall be sure of a comfortable journey. If he will accept the nomination(提名), a lot of electors will vote for him. 要知道这种带“will + 不定式”的if-分句在某些场合是不可以随便用的，比如我们可以说：If he gets my letter in time, hell be able to change his plans. 却不可以说：If he will get me letter in time, hell be,第二种类型：真实条件语句的主体,第二种类型：真实条件语句的主体,在if-分句中用 would ，有表示“意愿”的意思，常用语客气的请求，这时，主句动词既可以用 will / shall + 不定式， 也可用 would / should / could / might + 不定式 Eg: If you would kindly wait a moment, Ill see what I can do. If you would try Italian food, you would like it. 如果表示“意愿”的would不是用于客气的请求，那么，在一定上下文中也可能表示不大可能实现的“意愿”，这就属于非真实条件句，即第三种类型的条件句的一种变体形式。 3. 替换形式(Alternative Form) Set your alarm clock, and you wont oversleep. = If you set your alarm clock, you wont oversleep. Set your alarm clock, or (else) youll oversleep. =If you dont set your alarm clock, youll oversleep.,第三种类型：非真实条件句 Unreal Conditional,基本形式： (If) simple past / were + (Main) would, etc + inf Eg: If we caught the 10 oclock train, we would (could, might, etc) get there by lunch-time. if-分句说表示的条件在说话人看来实现的可能性不大，但还是有可能的，比如说话时间已经是九点多钟，尚未动身，因而不大可能赶上十点钟的火车，也不大可能在吃午饭以前到达。 If I came into a fortune, I would give up working. if-分句表示的条件came into fortune 显然是一种主观臆想，几乎不可能实现。 If I knew how it worked, I could tell you what to do. if-分句所表示的条件根据上下文显然与现在的事实相反。 变体形式：(If) were to + inf +(Main) would, etc + inf 要注意表示非真实条件的were to 与表示“义务”(Obligation)的am / is are to 和was / were to的区别：If he were to get in touch with me. I could explain. =Supposing he got in touch with me,(非真实条件) If he was to get in touch with me, why hasnt he done so? =If the arrangement was that he should get in touch with me, why?(表示“义务”) 另一种变体形式就是在从句中用would + 不定式，表示不大可能实现的“意愿”。,第四种类型：与过去事实相反的非真实条件句,基本形式:(If) had + -ed 分词 + (Main) would (could, might, etc) have + -ed 分词 Eg: We would / could / might have called you if we had known your telephone number. If we had caught that plane, we could have been taking part in the celebrations. 第三种类型与第四种类型的条件句的动词形式有相对的固定性，若要混合使用，则要注意句子的逻辑性。比如可以说： If you had told me to, I would have paid him. 却不可以说：If you told me to, I would have paid him. 这个句子的前半段（即从句）是第三种类型的条件句表示现在不大可能实现的条件，而后半段（即主句）却表示与过去事实相反的情况，前后在逻辑意义上不相协调。但是在保证句子合乎逻辑的前提下，也可根据语义意图混合使用两种句型的动词形式。 Eg: If writing had never been invented, we would have had no books. If writing had never been invented, we would have no books. 变体形式： (If) were to have + -ed 分词 + (Main) would (could, might, etc) have + -ed 分词 Eg: If you were to have asked me, I would have been only too willing to help. If you were to have explained your problem to me, I would have been able to help you.,Exercise,1.The volleyball match will be put off if it . will rain B. rains C. rained D. is rained. 2. Were it not for the snowy weather, we _all right. A. would be B. would have been C. were D. may be 3._more careful, his ship would not have sunk. A.If the captain were B. Had the captain been C. Should the captain be D. If the captain would have been 4. _today, he would get there by Friday. A.Would he leave B. Was he leaving C. Were he to leave D. If he leaves 5. _ she _ yesterday, she would meet the famous singer today. A. If, didnt leave B. Had not, left C. Hadnt, left D. Didnt, leave,Exercise,如果不是闰年（leap year），二月份有多少天？ How many days are there in February if it is not a leap year? 如果这没有许多蚊子，晚会就十全十美了。 If there werent so many mosquitoes, it would be a perfect evening. 如果你处于我的地位，你会怎么处理这个问题？ What would you do about