if引导的条件状语从句(讲义)

if引导的条件状语从句（讲义）
状语
用来表示行为发生的时间、地点、目的、方式、程度等，通常由副词或介词短语充当，也可由一个句子充当。

I slept at home yesterday because I had a bad cold.
状语从句
状语从句指句子作状语。

根据其作用可分为时间、地点、原因、条件、目的、结果、让步、方式等从句。

状语从句一般由连词(从属连词)引导。

I will go to school by bike tomorrow if it is sunny.
Grammar focus
—I think I’ll take the bus to the party.
—If you do, you’ll be late.
If you take the bus to the party, you’ll be late.
—I think I’ll stay at home.
—If you do, you’ll be sorry.
If you stay at home, you’ll be sorry.
—What will happen if they have the party today?
—If they have it today, half the class won’t come.
—Should we ask people to bring food?
—If we ask people to bring food, they’ll just bring potato chips and chocolate.
1.if在本单元句中意为“________；________”，用于引导_________________。

即if引导的是一个完整的句子，所以一定要有主谓，成为从句，另一个句子则成为主句。

If you go there, I’ll go, too.
We will go hiking if it doesn’t rain tomorrow.
If Bob leaves tomorrow, I will hold a party for him tonight.
2.if引导的条件状语从句既可以放在主句前，也可放在主句后。

但是如果放在主句前，即
句首时，从句后面要用______与主句隔开。

You will keep healthy if you do more exercise.
If you do more exercise, you will keep healthy.
3.时态：if引导的条件状语从句用________________表示将来，主句可以使用一般将来时，
含有情态动词的句子或者祈使句。

主将从现
If you practice speaking English more, you will like it better.
If she goes to New York tomorrow, I will go there, too.
My sister will be very happy if our uncle comes next week.
练习：
If Nancy ______ the exam, she will go to Australia for English study.
A. pass
B. passed
C. passes
D. will pass
If the weather ______ fine, we______ have a sports meeting next weekend.
A. will be; will
B. is; will
C. was; would
D. was; will
主情从现
If you get up at six tomorrow morning, you can catch the first bus.
If you go to study in America next year, you must learn English hard.
主祈从现
Let’s go out for a walk if it doesn’t rain tomorrow.
If you see a snake in the forest, don’t move!
unless
也可引导条件状语从句，表示“如果不，除非”
Unless he comes here in an hour, I will go there alone.
If he doesn’t come here in an hour, I will go there alone.
You will feel worse unless you go to see the doctor right now.
You will feel worse if you don’t go to see the doctor right now.
练习：
______ you read it, you can’t imagine how interesting the story is.
A. Unless
B. Because
C. Although
D. If
—Please give Alice the story book ________ you see her.
—All right.
A. unless
B. or
C. but
D. if Exercises
一、单项选择
( )1.Studying in groups is necessary ______ you want to do well in school.
A. if
B. until
C. unless
D. though
( )2.—Will you help me with the trouble?
—I won’t ______ you tell me the truth.
A. if
B. but
C. after
D. unless
( )3.If Bob ______ away from the junk food, he will be in good health.
A. stay
B. will stay
C. stays
D. stayed
( )4.If Tom _____ the game, we’ll give him a surprise.
A. win
B. wins
C. won
D. winning
( )5.We’ll go to the park if it _____ tomorrow.
A. won’t rain
B. don’t rain
C. doesn’t rain
D. rain
( )6.If you’re more careful, you ______ much better.
A. do
B. will do
C. are doing
D. did
( )7.If there ______ no buying and selling of animals, there _____ no killing in nature.
A. is; will be
B. will be; will be
C. is; is
D. will be; is
( )8.I’m waiting for my friend. If he _______, I _______ swimming alone.
A. doesn’t come; go
B. won’t come; go
C. won’t come; will go
D. doesn’t come; will go
二、翻译
9.如果明天不下雨，我会去看你的。

If it ______________ tomorrow, I ______________ you.
10.如果Mary不为考试做准备，她会不及格。

If Mary _____________________ the exam, she ______ fail the exam.
11.如果你不告诉我原因，我会告诉妈妈这件事。

_________________________________________________
12.我不会去医院的，除非你和我一起去那儿。

_________________________________________________
【参考答案】
Grammar focus
1.如果；假如；条件状语从句
2.逗号
3.一般现在时
主将从现
练习：
C B
unless
练习：
A D
Exercises
一、单项选择
1-5 ADCBC 6-8 BAD
二、翻译
9.doesn’t rain;will visit
10.doesn’t prepare for; will
11.If y ou don’t tell me the reason, I will tell mom this thing.
12. I won’t go to the hospital unless you go there with me.。