初中英语If引导的条件状语从句

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, 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：Let's go out for a walk unless you are too tired.

=If you are not too tired, let's go out for a walk.

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 。

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总结

IF引导的

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 sth unless sb does sth

if sb does not do sth

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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 don’t hurry up, you ____ catch the early bus.

5.Study hard, or you’ll miss fall behind.（同义句转换）

______ you study hard, you______ fall behind.

6.If you don’t put on your scarf, you’ll catch cold. （同义句转换）

Put on your scarf, _____ you’ll catch cold.

7.I don’t know if it_______ tomorrow. ）(表是否，用将来时态) If it ____ ,I won’t go shopping. (rain)（表如果，用现在时态）

8.I want to know if he _________(come) tomorrow, if he _______(come), 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.I’m sure if he _____(go) to the party, he________ (have)

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a great time.

11.If the rain _______(stop) tonight, we will go to the cinema.

12.I’ll buy a computer if I ______(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.Shall I say “Hello” when the foreigner ______(come) into the classroom?

19.He’l l get better grades if he _________ (study )hard.

20. If you work really hard, you _______ (be) famous and rich.

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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/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.Don’t wait for me if I (am/ will be) late.

6.They (won’t/don’t) 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 mu seum if he (won’t / don’t/ doesn’t) get tired?

9. Where (will/ do/does) they live if they (will miss/ miss/ misses) the bus?

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 _________( feel) glad.

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