Unit 4 Don't eat in class.
第2课时 Section A(Grammar Focus—3c)
一、祈使句
1．含义：祈使句是用来表示请求、命令或建议等的一种句型。其主语一般为第二人称you，但通常省略。祈使句的句末一般用句号，表示较强语气时用感叹号。为了使祈使句显得更委婉、有礼貌，可在开头或结尾加上please。
2．祈使句的五种类型
Do型
祈使句
实义动词原形＋其他
Listen to me，please.
请听我说。
Be型
祈使句
be动词＋其他
Be quiet，please.
请安静。
Let型
祈使句
Let＋sb.＋动词原形＋其他
Let's play football.
让我们踢足球吧。
Please型
祈使句
Please＋动词原形＋其他
Please stand up.
请起立。
Please don't stand up.
请不要起立。
No型
祈使句
No＋v．－ing/名词！(表示禁止)
No smoking!
禁止吸烟！
No photos!
禁止拍照！
3.祈使句的否定形式
通常是在谓语动词前加don't。但要注意以let开头的祈使句，其否定形式是 “Don't＋let＋宾语＋动词原形＋其他．”或“Let＋宾语＋not＋动词原形＋其他”。
4．对祈使句的基本回答：
(1)A：Tom, take the box to Mr.Wu's office.
B：肯定回答——Yes, I will.
否定回答——Sorry, I can't carry it.
(2)A：Don't listen to music in class.
B：No, I won't.(用于自己之前没做过，同时也表明自己今后也不会做时)或Sorry, I won't do it in future.(用于自己犯错，被别人禁止时)
(3)A：Let's go out for a walk.(“Let's do sth.”常用于提出建议)
B：肯定回答——That's a good idea.或That sounds good.(直接表示赞同)
否定回答——Oh, no.It's too hot.或Oh, no.Let's watch TV at home.(可用“No”作否定回答，并适当解释或提出自己的见解)
祈使句一般要对方去做的动作是在将来发生。肯定回答时常用“Yes, I will”；否定回答时常用“No, I won't”等。will为“将要”之意，won't为will和not的缩写形式，为“将不；将不会”之意。
二、情态动词can与have to
1．can能；会
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(1)表示做某事的能力，其否定式为can't。如：
Can you speak English?
你会讲英语吗？
(2) 表示“允许；许可”。如：
You can keep the book for a week.
这本书你可以借一周。
2．have to必须；不得不
其后接动词原形。have to有第三人称单数形式，即has to，变疑问句和否定句时要借用助动词do/does。如：
We have to go home after school.
我们放学后必须回家。
Ⅰ.用括号内所给单词的适当形式填空。
1．__Don't__play__(not play) with fire(火)．
2．Don't __run__(run) in the classroom.
3．Let him __not__play__(not play) the computer games.
4．Can we __eat__(eat) here?
5．Do you have to __go__(go) to bed before ten at night?
Ⅱ.根据汉语意思完成句子，每空一词。
1．到这儿来。
__Come__ __here__．
2．别在走廊里跑。
__Don't__ __run__ in the hallways.
3．快点！
__Be__ __quick__！
4．不要在这儿吃东西。
__Don't__ __eat__ here.
5．让我们骑自行车到那儿吧。
__Let's__ __ride__ the bike to get there.
Ⅲ.按要求完成下列句子，每空一词。
1．Lily can play the guitar.(改为一般疑问句并作否定回答)
—__Can__ Lily __play__ the guitar?
—No , she __can't__．
2．Jack has to play the piano every weekend.(改为一般疑问句)
__Does__ Jack __have__ __to__ play the piano every weekend?
3．Be quick.(改为否定句)
__Don't__ __be__ quick.
4．You can't eat food in class.(改为祈使句)
__Don't__ __eat__ food in class.
5．You can't be late for class next time.(改为祈使句)
__Don't__ __be__ late for class next time.
Ⅳ.单项选择。
(C)1.________ listen to music in the classroom.
A．Not B．No
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C．Don't D．Doesn't
(A)2.Tom，please ________ the classroom now.
A．clean B．to clean
C．cleans D．cleaning
(A)3.Let's ________ on time for classes.
A．be B．be not
C．are D．is
(B)4.She has to ________ her homework every night.
A．does B．do
C．doing D．did
(A)5.Sorry，you ________ play basketball in the classroom.
A．can't B．don't
C．don't have to D．doesn't
Ⅴ.选词填空。
阅读短文，从方框中选择适当的词并用其正确形式填空，使短文通顺、意思完整。每词限用一次。
fight dirty dish rule before
follow outside keep one practice
Dear Sam，
Here are some __1__ for you when your dad and I are not at home.__2__， get home early.Don't play __3__ after school.Second，take care of(照顾) your brother and don't __4__ with him.Third, help your grandma do the __5__ after dinner.Fourth，remember to __6__ the piano for one hour every evening.Fifth，go to bed __7__ 10 o'clock.The last one, __8__ your room clean and don't leave your __9__ clothes everywhere.Your dad and I will be very happy if you can __10__ the rules.
1．__rules__ 2.__First__ 3.__outside__
4．__fight__ 5.__dishes__ 6.__practice__
7．__before__ 8.__keep__ 9.__dirty__
10．__follow__
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