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一、条件状语从句
一）
if
引导的条件状语从句
（
if
意思为
“
如果
”
，主将从现）
用
法
①
主句为一般将来时态，
if
从句用一般现在时态
（即主将从现）。
②
主句中含有情态动词，
if
从句用一般现在时态。
If you finish your homework, you can go home
例
句
We will stay at home if it rains tomorrow.
now.
③
主句为祈使句，
if
从句用一般现在时态。
Don’t jump into the river if you feel very hot.
如果我是你，我就不会那么做的。
If you gave me some money, I would be
veryhappy.
如果你给我一些钱，我就会很高兴的。
④
主句为过去将来时，
if
从句用一般过去时态
（如
If I were you, I wouldn’t do it like that.
果涉及到
be
动词，一律都用
were
）。此时，表
达的是和现实相反的推测 ，用虚拟语气。
A
：
if
条件句的时态搭配
1
．
if
从句用一般现在时，主句用一般将来时
(
如果表示可能发生的事
)
If he runs he’ll get there in time.
If you go to bed earlier, you won’t feel tired next morning.
2
．
if
从句用一般现在时，主句用
may/might/can/ must/should
If the fog gets thicker the plane may/might not take off.
If it stops snowing we can go out.
If you want to lose weight you must/should eat less bread.
3
．
if
从句用一般现在时，主句用一般现在时
(
如果表示必然发生的事情
)
If you heat ice it turns to water.
如果把冰加热，它就会化成水。
If bears are in danger ,they attack people.
If you drop a glass, it breaks.
B:
引导的条件状语从句的用法总结
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。
在
if
引导的条件状语从句中，
if
和条件句位置灵活，但不管怎样，一定要学会冷静分析
句意和句子结构。
特别提醒：
If
只有当作为
“
如果
”
的意思时，才符合
主将从现
原则；
如果
If
作为
“
是否
”
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的意思时，则不符合
主将从现
原则。
二）
unless
引导的条件状语从句，意思相当于
if....not... ,
语气比较强。
（主将从现）
You’ll fail the exam unless you study hard.
=You’ll fail the exam if you don’t study hard.
三）
so/as long as
引导的条件状语从句，表示
“
只要
”
（主将从现）
As long as I know the money is safe, I won’t worry about
it.
As long as it doesn’t rain, we can play football.
二、时间状语从句
以
when
，
before
，
as soon as
，
once
等引导的适用
“
主将从现
”
原则
I'll tell my mother the good news when she comes back.
she will call you as soon as she returns.
Once you see the film, you will never forget it.
一旦你看了这部电影，
你将永远不会忘记。
三、
If
条件句的同义句
1.
借助
“
祈使句
+and /or+
简单句
”
，其中
and
表示句意顺承，
or
表示转折。
If you work hard, you will pass the exam.
= Work hard ,and you will pass the exam.
If you don’t hurry up. you will be late.
=Hurry up, or you will be late.
2.
借助介词
with
或
without
来转换。
If you help me, I’ll finish my job soon.
=With your help, I’ll finish my job soon.
If you don’t give me a hand, I ‘ll not complete it in such a short time.
= Without your help, I won’t complete it in such a short time.
课堂训练：
1)
勾选正确的答案完成句子。
( 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 there (will be/ are/is) a car accident, they (will call/call/calls) 110 for help at once.
4. If it (won’t/don’t/doesn’t/ isn’t) rainy, we (will take/ take/takes) walk outside.
5. If a UFO (will land/land/lands) in front of me, I (will go/go/goes) in to look for the alien.
6. If he (will have/have/has) money, he (will build/build/builds) a science lab.
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’t wait for me if I (am/ will be) late.
(won’t/don’t) go to the beach if it (will rain/rain /rains).
9. I (will call/ call) you if he (will stay/stay /stays) at home.
10. Mr Smith (will let/ let/lets) you know if he (will need/ need/ needs) help.
11. (Will / Do/ Does) he visit the museum if he (won’t / don’t/ doesn’t) get tired?
12. Where (will/ do/does) they live if they (will miss/ miss/ misses) the bus?
2)
用所给词的适当形式填空
you ________(feel) tired, you _______________ (have) to have a rest.
2. Where _______ he _________(see) the film if he ________________(have) time?
3. If there __________(be) fewer trees, there _______________( be) more pollution.
4. He _________(dress)
more casually if he _____________( not work) on weekends.
5. If Marcia _____________(live) alone, she ___________________( keep) a pet parrot.
6. Lana ____________( buy) a new dress if the old one ____________(be) out of style.
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.
11.I ____________(go) to the beach if it________________ ( not rain) this week.
12. ________they ________( have) a match if the P.E. teacher ___________(be) busy?
____(write) a letter to his grandparents if he ____(get) his report card this week.
14. If she ____________(get) up late, she _____________ ( not catch) the early bus.
15. Peter ________(major) in English if he ____(pass) the exams in Peking
University.
16. What will you buy if you ________
（
have
）
a lot of money?
17. If it ________
（
not snow
）
tomorrow, we will feel unhappy.
18. You mustn’t go to school if you ________
（
be
）
still in bed.
19. If he _______
（
be
）
at home at that time, he would know it.
20. Please show me the way if you ________
（
know
）
it.
21. You will hurt your teeth if you ________
（
eat
）
too much candy.
22. If you gave me a toy car, I _________
（
be
）
very happy.
23. I would get the prize if I _________
（
work
）
hard.
24. I don't know if you
(come) tomorrow.
25. I don't know if you
(like) this present.
3)
按照中文意思完成英文句子
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