1、（1）真实条件句表示提出的假设完全可以成为事实,谓语动词用陈述语气.If time permits,well go fishing together.如果有时间的话，我们就一起去钓鱼。（2）虚拟条件句表示所提出的假设实现的可能性极小与事实相反,谓语动词用虚拟语气.虚拟语气也可以表示愿望,请求及建议等.If it had rained yesterday,we would have stayed at home.如果昨天下雨的话，我们就会留在家里。一、与现在事实相反的假设从句：if+主语+动词的过去式(be 用 were)+主句：主语+would(should,could,might)+动词原形
2、+If I were you,I would go with him.If I were you,I should buy it.注意：如果动作在进行中，主句要用：主语+would be+进行式动词+If they were here,he would be speakingto them now.二.与过去事实相反的假设从句：If+主语+had+过去完成式动词+主句：主语+would(should,could,might)+have+过去完成式动词+If you had studied harder last term,you could have passed exam.If it had
3、 snowed,I would have skied in the park.注意：如果动作在进行中，主句要用：主语+would+have+完成进行式动词+If they had been here,he would have been speaking to them.三.与将来的事实可能相反从句：If+主语+should(或were)+动词原形+主句：主语+would(could,should,might)+动词原形+If it should rain,the crops would be saved.If he were here,I would give himthe books.注意
4、：如果动作在进行中，从句(不是主句)要用：“If+主语+过去进行式动词+If she were staying here now,I would let her ride my horse.四.从句的 If 有时可省略，那么从句中的动词(were,had,should)就得移到主语前面：原句：If he had tried it,he could have done it.去If：Had he tried it,he could have done it.五.有时虚拟条件句的从句和主句地动词动作时态会不一致：1)从句表示过去，主句表示将来：If they had started the ear
5、ly morning yesterday,they would be here now.2)从句表示将来，主句表示过去：If I were not to make a preparation for my experiment this afternoon,I would have gone to see the film with you last night.3)从句表示过去，主句表示将来：If we hadnt made adequate preparations,we shouldnt dare to do the experiment next week.4)从句表示将来，主句表示现
6、在：If we shouldnt have an exam this afternoon,I would go shopping now.Give your own answers to the questions.If you could clone a man,would you do it?Yes,I would./No,I wouldnt.2.If you were a scientist,would you work for a cloning company?3.If you had the money,would you pay scientists to clone you?4
7、.If cloning became easy,would that be a good thing,in your opinion?1.If you were head of the government,would you allow cloning?1.If scientists _(clone)me,I _(feel)very strange.would feelcloned2.If governments _ (not allow)cloning,many scientists _(be)very angry.would bedidnt allow3.If I _(meet)a cl
8、oned copy of myself,I _ (run away)!would run awaymet4.If cloning _(be)easy,the world _(be)a very different place.would bewere/was5.If cloned animals _(live)until they _(be)old,scientists _(be)very pleased.would belived wereI have known my friend Robin(1)_ many years and am very fond(2)_ him,but he h
9、as some strange ideas.For example,he says that if he(3)_ the money,he(4)_ ask scientists to clone him.When I ask himforofhadwould(5)_ he would like this,he replies that he(6)_ love to meet an identical copy of himself.I dont feel the same at all.If I(7)_ an identical copy of myself,I(8)_ run as fast
10、 as I could in the opposite direction.I cant think of anything(9)_ awful!But Robin has other strange ideas.For example,would whywouldmet/sawmorehe says that(10)_ scientists allowed him,he would(11)_ to the moon.When he says this,I reply that if it(12)_ possible I(13)_ like to live to be two hundred.
11、“Me too,”Robin replies.(14)_he knows I am joking.The problem is,I know he is serious.If he a dreamer or(15)_ his dreams become possible one day?I have no idea.ifgo/fly/travelwerewould but could1.If you hadnt gone with Tom to the party last night,_.a.you would meet John already b.you wont have missed
12、 John c.you will have met John d.you would have met John2.Supposing this ship _,do you think there would be enough life jackets for all the passengers?a.was sinking b.has sunk c.were to sink d.sunk3.The insects would devour all our crops and kill our flocks and heads,if _ for the protection we get f
13、rom insect-eating animals.a.it is not b.it were not c.were it not d.they were not4.Frankly,Id rather you _ anything about it for the time being.a.do b.dont do c.didnt do d.will not do5.If I _ in the twenty-first century,I _ my vacation in a very different way.a.should livewould spend b.will live.should spend c.are living should have spent d.will be livingwould have spent6.Its high time you _.a.start to work b.would start to work c.started to work d.had started to work
