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1、初中英语if引导的条件状语从句在 if 引导的条件状语从句中，if 和条件句位置灵活，可直接放在主句后面，若 if 条件句放句首， 从句后面要加逗号，和主句隔开。还要注意前后时态一致原则.引导条件状语从句的连接词主要有：if(如果）、unless（除非）或 as long as（只要）等。unless在意思上等于if.not。 一、条件状语从句用法 1、引导条件状语从句最常用的连词是if,由if引导的条件状语从句表示在某种条件下某事很可能发生。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,
2、you will let him down.如果你考试不及格,你会让他失望的。 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。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。 2、unless = if.not. 除非,若不,除非在的时候 例如：Lets go out for a walk unless you are too tired. =If you are not too tired, lets go out for a walk.
3、 Unless it rains, the game will be played.除非下雨,比赛将照常进行。 二、时态问题 在条件状语从句中，要注意“主将从现”的规定，即主句用一般将来时，从句用一般现在时表示将来时。例句：I will come to see you if I have time. 我有时间，我就来看你。三 如果 if 条件句谈论的是重复发生和预示要发生的情景和事件，则主从句大多用一般现在时态。如： If bears are in danger ,they attack people.误区提醒 if 既可以引导条件状语从句，表示“如果”，也可以引导宾语从句，表达“是否”。辨别
4、它在这两种从句中的时态是我们经常容易出错的地方。另外，if 和unless的用法也需注意。 典型例题： -I wonder if your wife to the party. -If your wife _, so will mine。. A. will go， go B. will go, goes C.goes, will go D. will go, will go 解析：第一句中if表示“是否”，引导宾语从句，用将来时will go；第二句“如果你的妻子去，我的妻子也去”，if引导条件状语从句，用一般现在时表示将来时。 your wife，单三人称主语，所以用goes 。总结IF引导
5、的 一、表示将来可能发生的： (1) If sb does sth, sb will do sth = sb will do sth if sb does sth 主句一般将来时 从句一般现在时(2)主句为祈使句或情态动词形式If sb does sth, please do sth If sb does sth, sb may(情态动词) do sth 二、表必然发生的If sb does sth, sb/sth does sth = sb/sth do sth if sb does sth 主句一般现在时， 从句一般现在时（相当于when引导的从句）Unless引导的sb will do
6、sth unless sb does sth if sb does not do sth 练习1.He _ (fail) in the exam if he _ (not study) hard.2.Unless you _ (leave) now, you _(be) late.3.We _ (have) a barbecue unless it _ (rain) .4.Hurry up, or you will miss the bus.（同义句转换） _ you dont hurry up, you _ catch the early bus.5.Study hard, or youll
7、 miss fall behind. （同义句转换） _ you study hard, you_ fall behind.6.If you dont put on your scarf, youll catch cold. （同义句转换） Put on your scarf, _ youll catch cold.7.I dont know if it_ tomorrow. ）(表是否，用将来时态)If it _ ,I wont go shopping. (rain) （表如果，用现在时态）8.I want to know if he _(come) tomorrow, if he _(co
8、me), I _(give) the massage to him. 9. Please let us know if he _(arrive) tomorrow. 请告诉我们他明天是否会来 Please let us know if he _ (arrive) tomorrow.如果他明天来的话请告诉我们10.Im sure if he _(go) to the party, he_ (have) a great time.11.If the rain _(stop) tonight, we will go to the cinema.12.Ill buy a computer if I _
9、(have) enough money.13.You _(not get) nervous if you _(do ) enough exercise.14.If she _ (be) kind to me , I _(not argue) with her.15.If you _(pay) more attention to that, he _ (not get) injured.16.Mr Li will be mad if we _(break) the rules.17. If it _ (be) cloudy, they _(not go) there by air.18.Shal
10、l I say “Hello” when the foreigner _(come) into the classroom?19.Hell get better grades if he _ (study )hard.20. If you work really hard, you _ (be) famous and rich.if 条件状语从句的时态练习 一在正确的答案下划一条线。1.Daina ( will go/go/goes) to Europe if she (will pass/pass/passes) the exams .2. The graduates (will teach
11、/teach/teaches) in the poor village if the Ministry of Education (will agree/ agree/agrees) soon.3. If a UFO (will land/land/lands) in front of me, I (will go/go/goes) in to look for the alien.4. If he (will have/have/has) money, he (will bulid/build/builds) a science lab.5.Dont wait for me if I (am
12、/ will be) late.6.They (wont/dont) go to the beach if it (will rain/rain /rains).7. I (will call/ call) you if he (will stay/stay /stays) at home.8. (Will / Do/ Does) he visit the museum if he (wont / dont/ doesnt) get tired?9. Where (will/ do/does) they live if they (will miss/ miss/ misses) the bu
13、s?二、用所给词的适当形式填空1.If you _(feel) tired, you _ (have) to have a rest.3. If there _(be) fewer trees, there _( be) more pollution.5. If Marcia _(live) alone, she _( keep) a pet parrot.6. Lana _( buy) a new dress if the old one _(be) out of style.7.The twins _(fight) if they_(argue).8. I _(have) a bake sale if I _(need) money for education.9. Peter _( send) me a beautiful souvenir if he _(tour) Spain.10. If Mr Green _(say) I am hard- working, my parents
