1、单元语法小专题(Grammar Focus)语法精讲if 引导的条件状语从句条件状语从句通常由连词 if 引导,意为“如果;假如;倘若” ,表示在某种条件下,很可能会发生某种事情或不发生某种事情。1if 条件状语从句的位置在 if 引导的条件状语从句中,if 条件句位置比较灵活,可放在主句前面也可放在主句后面。若放在主句前,从句后面要用逗号和主句隔开。如:If he doesnt feel tired,he will visit the museum.He will visit the museum if he doesnt feel tired.如果他不感觉累,他就去参观博物馆。2if 条件
2、状语从句的时态搭配(1)当主句用一般将来时,if 引导的条件状语从句要用一般现在时。如:If it rains tomorrow,I wont climb the hills.如果明天下雨,我就不爬山。(2)当主句中含有 can,may,must 等情态动词时,if 引导的条件状语从句要用一般现在时。如:We can win the basketball game if he joins us.如果他加入我们,我们就能赢这场篮球赛。(3)当主句是祈使句时,if 引导的条件状语从句要用一般现在时。如:Help your mom with the housework if you finish y
3、our homework early.如果你完成作业早,就帮你妈妈做家务。if 条件状语从句用法歌诀:if 条件句不一般,几个要点记心间;条件句,放在前,逗号要放句中间;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。3与其他句式之间的转换(1)借助“祈使句 and/or 一般将来时的句子”这一句型来转换。and 在句意上表示顺承关系,or 表示转折关系。如:If you get up early,youll get there on time. Get up early,and youll get there on time.Get up early,or you wont
4、get there on time.早点起床,你就会准时到那里。(2)借助介词 without 或 with 来转换条件状语从句。如:If there is no water,fish will die.Fish will die without water.如果没有水,鱼就会死。If you help me,Ill finish the work soon.With your help, Ill finish the work soon.如果你帮助我,我就会快点完成工作。(3)if not 引导的条件状语从句,可以借助连词 unless 来改写。如:You will be late if y
5、ou dont go there by bus.You will be late unless you go there by bus.如果你不乘公共汽车你就会迟到。语法精练.用括号内所给单词的适当形式填空。1If it rains tomorrow,I _(stay) at home.2He will take a trip to Beijing if he _(be not) busy next week.3Please tell Li Jun about it if he _(come) back.4If you dont wear your school uniform to the
6、party,the teachers _(not let) you in.5She _(not go) shopping with her parents if it snows this afternoon.单项选择。( )6.Do you know when he will come back tomorrow?Sorry,I dont know.When he _ back,Ill tell you.Acomes Bwill comeCcome D may come ( )7.Mary will go to Sanya if she _ a fiveday trip.Ahave Bhad
7、Cwill have Dhas( )8.What will you do if you _ to the party without invitation?Ago Bwent Cgoing Dwill go ( )9.If I eat too much food, I _ too fat.Aam Bwas Cwill Dwill be( )10.Ill give the book to him if he _ here next Sunday.Awill come BcomesCis coming Dcame.同义句改写,每空一词。11Study hard,or you wont pass t
8、he exam.If you study hard,you _ _ the exam.12Take a taxi,and youll catch the train._ you _ a taxi,youll catch the train.13If you dont help me,I cant catch up with the others.I cant catch up with the others _ _ _14We will be late for the meeting if we dont be quick.We will be late for the meeting _ _ _ _15If you are late,the teacher will be angry._ _ late,_ the teacher will be angry.单元语法小专题(Grammar Focus).1.will stay 2.isnt es 4.wont let 5.doesnt go.610 ADADB.11.will pass 12.If;take 13.without your help 14.unless we are quick 15.Dont be;or