主将从现常见的有以下六种情况.doc

常见的有以下六种情况：一、如果主句是将来时或表示将来含义时，那么条件和时间状语从句多用一般现在时如： When I grow up, I will be a nurse and look after patients/ I want to be a nurse and look after patients.我长大后要当一名护士，照顾病人。二、如果主句是祈使句，那么从句通常要用一般现在时如：Dont laugh at me when I make a mistake.我犯错误的时候不要笑话我。三、如果主句是含有情态动词的一般现在时，根据需要从句多用一般现在时如：You should be quiet when you are in the reading room在阅览室时应保持安静。四、 如果if的条件状语从句遇到变换间接和直接时 , 祈使句应用notto.如; She said not to close the window常见的时间状语从句的连词有：as soon as,when,while ,as,until等五、主将从现说的是在含有时间状语从句和条件状语从句的主从复合句中，如果主句的时态是一般将来时，那么从句要用一般现在时。例如：I will tell him about it when he comes.If it is fine tomorrow, we will go outing.六、如果主句的时态是过去将来时，那么从句要用一般过去时 。例如：He said that he would have another try if he had the chance.I knew he could help me if he was free the next day.主要标志有：if 、unless 、until、 when 、as soon as等If引导的条件句（if翻译成如果的时候）.(if 从句) 主句v./ v.三单 will+v. if+sb+v./ v.三单 can+v.某事很可能发生，条件是可能存在的，主句中某种情况发生的概率也是很高的。如：If you ask him，he will help you如果你请他帮忙，他会帮你的。If you fail in the exam，you will let him down如果你考试不及格，你会让他失望的。If you have finished the homework， you can go home如果你作业做完了就可以回家了。另外，if从句还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，表示对现在或过去的一种假设。如：If I were you，I would invite him to the party如果我是你，我会邀请他参加聚会。I would have arrived much earlier if I had not been caught in the traffic要不是交通堵塞，我本会来得早一些。另外你还要注意if 条件句的时态搭配：1if从句用一般现在时，主句用一般将来时If he runs hell get there in time. 如果他用跑的，他就会及时赶到那儿。The cat will scratch you if you pull her tail. 如果你拉猫的尾巴，它就会抓你。2if从句用一般现在时，主句用may/might/canIf the fog gets thicker the plane may/might be diverted. 如果雾在大一些，飞机可能就会改在别的机场降落。If it stops snowing we can go out. 如果雪停了，我们就可以出去。3if从句用一般现在时，主句用must/shouldIf you want to lose weight you must/should eat less bread. 如果你想减肥，你必须少吃面包。4if从句用一般现在时，主句用一般现在时If you heat ice it turns to water. (也可用will turn)如果把冰加热，它就会化成水。5if从句用现在进行时，主句用一般将来时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。6if从句用现在完成时，主句用一般将来时If you have finished dinner Ill ask the waiter for the bill. 如果你吃完了，我就叫服务生来结账。