if条件句和should的用法.doc

If 引导条件句的用法1、真实条件句用于陈述语气，假设的情况可能发生，其中 if 是如果的意思。 时态关系 句型： 条件从句 主句 一般现在时 shall/will + 动词原形 If he comes, he will bring his violin. 典型例题 The volleyball match will be put off if it _. A. will rain B. rains C. rained D. is rained 答案B。真实条件句主句为将来时，从句用一般现在时。 注意： 1） 在真实条件句中，主句不能用be going to表示将来，该用shall, will. (错) If you leave now, you are never going to regret it. (对) If you leave now, you will never regret it. 2） 表示真理时，主句谓语动词便不用shall (will) +动词原形，而直接用一般现在时的动词形式。 2 非真实条件句 1）时态：可以表示过去，现在和将来的情况。它的基本特点是时态退后。 a. 同现在事实相反的假设。 句型 ： 条件从句 主句 一般过去时 should( would) +动词原形 If they were here, they would help you. b. 表示于过去事实相反的假设。 句型： 条件从句 主句 过去完成时 should(would) have+ 过去分词 If she had worked harder, she would have succeeded. The rice would not have been burnt if you had been more careful. If my lawyer had been here last Saturday, he would have prevented me from going. If he had come yesterday, I should / would have told him about it. 含义：He did not come yesterday, so I did not tell him about it. If he had not been ill and missed many classes, he would have made greater progress. 含义： He was ill and missed many lessons, so he did not make greater progress. c. 表示对将来的假想 句型： 条件从句 主句 一般过去时 should+ 动词原形 were+ 不定式 would + 动词原形 should+ 动词原形 If you succeeded, everything would be all right. If you should succeed, everything would be all right. If you were to succeed, everything would be all right. 3 混合条件句 主句与从句的动作发生在不同的时间，这时主，从句谓语动词的虚拟语气形式因时间不同而不同，这叫做混合条件句。 If you had asked him yesterday, you would know what to do now. （从句与过去事实相反，主句与现在事实相反。） If it had rained last night (过去), it would be very cold today (现在). 4 虚拟条件句的倒装 虚拟条件句的从句部分如果含有were, should, 或had, 可将if省略，再把were, should或had 移到从句句首，实行倒装。 Were they here now, they could help us. =If they were here now, they could help us. Had you come earlier, you would have met him =If you had come earlier, you would have met him. Should it rain, the crops would be saved. =Were it to rain, the crops would be saved. 注意： 在虚拟语气的从句中，动词be的过去时态一律用were，不用was， 即在从句中be用were代替。 If I were you, I would go to look for him. 如果我是你，就会去找他。 If he were here, everything would be all right. 如果他在这儿，一切都会好的。 典型例题 _ to do the work, I should do it some other day. A. If were I B. I were C. Were I D. Was I 答案C. 在虚拟条件状语中如果有were, should, had这三个词，通常将if省略，主语提前, 变成 were, should, had +主语的形式。但要注意，在虚拟条件状语从句中，省略连词的倒装形式的句首不能用动词的缩略形式。如我们可说 Were I not to do., 而不能说 Werent I to do. 5 特殊的虚拟语气词：should 1） It is demanded / necessary / a pity + that结构中的主语从句的谓语动词要用should 加动词原形， should 可省略。 句型： (1)suggested It is (2)important that+ (should) do (3) a pity (1)suggested, ordered, proposed, required, demanded, requested, insisted； + (should) do (2)important, necessary, natural, strange a pity, a shame, no wonder (3)It is suggested that we (should) hold a meeting next week. It is necessary that he (should) come to our meeting tomorrow. 2）在宾语从句中的应用 在表示命令、建议、要求等一类动词后面的从句中。 order, suggest, propose, require, demand, request, insist, command, insist + (should) do I suggest that we (should) hold a meeting next week. He insisted that he (should ) be sent there. 注意： 如suggest, insist不表示建议 或坚持要某人做某事时，即它们用于其本意暗示、表明、坚持认为时，宾语从句用陈述语气。 The guard at gate insisted that everybody obey the rules. 判断改错: （错） You pale face suggests that you (should) be ill. (对) Your pale face suggests that you are ill. (错) I insisted that you ( should) be wrong. (对) I insisted that you were wrong. 3）在表语从句，同位语从句中的应用 在suggestion, proposal, idea, plan, order, advice等名词后面的表语从句、同位语从句中要用虚拟语气，即（should）+动词原形。 My idea is that we (should) get more people to attend the conference. I make a proposal that we (should) hold a meeting next week.could, should和would除了分别是can，shall和will的过去式，还有其他的用法，有人学英语多年还容易将其搞混淆，因此使用时要特别注意： 1.could的用法 (1)表示惊异、怀疑、不相信等态度： How could John be so arrogant？约翰怎么这么傲慢？ He couldnt be over forty. 他不可能有40多岁了。 Where could she be now？ 她现在能在哪儿呢？ 以上三个句子可以用can代替could，两者在时间上没有差别，只是用could时语气较缓和，用can时不相信程度更强一些。 (2)比较委婉客气地提出问题或陈述看法： Could(Can) you lend me your walkman？你能把随身听借给我用一下吗？ Could I see your credentials？我可以看看你的证件吗？ 这时could和can没有时间上的差别。 (3)在虚拟条件句中作助动词，与谓语动词一起构成谓语： I could do it (if I would).（假如我愿意的话）我是能办到这一点的。（指说话人不愿意） You could have done better if you had been more careful. 你要是再细心一点，是可以做得更好的。2.should的用法 (1)表示惊异、赞叹、不满等情绪： It is simply a miracle that rice should grow in such a place. 稻子竟能在这样的地方生长，这实在是个奇迹。 Its wonderful that you should get full marks. 你得了满分真了不起。 Why should you be so late today？你今天怎么来得这么晚？ (2)表示委婉地陈述自己的意见： I should think you are right. 我想你是对的。 (3)（表示语气较强的假设）万一，竟然： If he should fail to come, ask Tom to work in his place. 万一他不来，就叫汤姆代替他工作。 (4)（表示可能性、推测）可能，该： My sister should be home by now. 我妹妹现在应该到家了。 (5)（表示建议、命令、愿意等）应该： I move that he should come with us. 我坚持他应和我们一起去。 3.would的用法 (1)用在虚拟语气的主句中： If you went to see him, he would be delighted. 如果你去看他，他一定非常高兴。 She would have come if she hadnt been so busy. 要不是忙她就来了。 (2)委婉地提出请求、建议或看法： Would you take a seat？ 请坐！ (3)表示意愿，在陈述语气和虚拟语气都可用： He would not leave before he finished his work. 他在完成工作以前不愿离开。 (4)表示过去反复发生的动作： Now and then a blackbird would call. 不时会有山鸟叫。 (5)表示过去的一种倾向: The wound would not heal. 伤口老不愈合。 (6)表示推测：That would be in spring 1989. 那大概是在1989年春天。should和would都是情态动词，也是助动词，你应该知道，它们两个有时也可以不译。 首先should，在汉语中，我们常译为：应该。 而would常译为：可以或者是将要。 给个例子you should clean the classroom。你应该打扫教室。 It would be rain soon 。 不久将会下雨。 而仅仅将这两个词做比较，显然should 比would语气更强烈 我今年刚高考完。还有几个需要提醒你，1个用法 sb shuold have done sth 某人应该做什么事（注意是应该，而实际上没做）。should和would的区别和用法 1）should无词义，只是shall的过去形式，与动词原形构成过去将来时，只用于第一人称。 例如：I telephoned him yesterday to ask what I should do next week. 我昨天给他打电话，问他我下周干什么。 比较：What shall I do next week? I asked. 我下周干什么？我问道。（可以说，shall变成间接引语时，变成了should。） 2） would也无词义，是will的过去形式，与动词原形构成过去将来时，用于第二、第三人称。 例如：He said he would come. 他说他要来。 比较：I will go, he said. 他说：我要去那儿。 变成间接引语，就成了： He said he would come. 原来的will变成would，go变成了come.。 should 本应该做某事却没有做,表示责备和遗憾. 如; You should ahve told me the news eariler. would 表示与事实相反。 1。If I were a bird, I would be happy.(与现在事实相反) 2. If I had told him the news, he would have cried.(与过去事实相反) 3. If I were to go tomorrow, I would take a plane.(与将来事实相反)should have done 是翻译为本该做某事 而没做 would have filled 没有这个意思 1 Like the rules governing the use of shall and will on which they are based, the traditional rules governing the use of should and would are largely ignored in modern American practice. Either should or would can now be used in the first person to express conditional futurity: 就象作为shall 和 will 词的基础的限用的用法规则一样， 适用于should 和 would 这个词的传统使用规则在现代美国英语中也已被忽略了。 现在should 或 would 这两个词中的任何一个都可以用于第一人称，表示条件式中的将来： If I had known that, I would (or somewhat more formally, should ) have answered differently. 如果已经知道了这个情况的话，我就（或正规一点用 should ） 不会那么回答了 ， 2 But in the second and third persons only would is used: 但在第二人称或第三人称中只用would ： If he had known that, he would (not should ) have answered differently. 如果他知道那个情况的话，就（不能用 should ） 不会那么回答了。 3 Wouldcannot always be substituted for should, however. Should is used in all three persons in a conditional clause: 但是Would并不是总是能由 should 代替。 Should 在三种人称的条件从句中都可以用： if I (or you or he ) should decide to go. 如果我（或 你 或 他 ） 决定要去。 4 Should is also used in all three persons to express duty or obligation (the equivalent of ought to ): Should用于这三种人称的表示职责和义务的句子中（相当于 ought to ）：I (or you or he ) should go. 我（或者 你 或者 他 ） 应该去 。 5 On the other hand, would is used