《Language in use》Help PPT课件4
祈使句
此类祈使句喑含的主语是you，但通常省略。句首或句末有时加please，还可以加上称呼语，用逗号与句子主体隔开。
祈使句表达说话人对对方的叮嘱、劝告、希望、禁止、建议、请求或命令等。祈使句一 般以动词原形开头，无时态和数的变化。
▲1. 动词原形构成的祈使句
肯定形式
Do型，即动词原形（+宾语）+其他
Be型，即Be+表语（名词或形容词）+其他
否定形式：动词原形前加don't，也可以用否定副词never开头。
Have a nice day! 祝你度过美好的一天！
Don’t waste your time! 别浪费时间 了！
Never be late again! 再也不要迟到 了！
Come this way please ! 请走这边。
Please be quiet, boys! 男孩们，请安静！
Make sure he’s warm. 确保他不受凉。
Don’t use the lift. 不要使用电梯。
... ... ...
▲2. let’s构成的祈使句
这类祈使句往往用于提出建议。
肯定结构：Let+宾语+动原+其他
否定结构：Don't let +宾语+动原+其他
Let+宾语+not+动原+其他
▲3. 无动词祈使句
祈使句还可用名词、形容词、副词以及以no开头的短语充当。
... ... ...
情态动词must, can, could表推测
▲用法区别
must
表推测时常用在肯定句中，语气较为肯定，此时must可以翻译成“一定；准是”。
can
表推测时常用在否定句或疑问句中，是有把握的否定推测，意为“不可能”。
could
可以用于肯定句、否定句或疑问句中，也可以表示过去的可能性，表示可能发生，程度比can弱。
请仔细对比下列一组句子
Who sent the present? Can it be your brother?
是谁送来的礼物啊？会是你哥哥吗？ （询问可能性）
It must be your brother. I saw him in your room just now.
肯定是你哥哥，我刚才看见他在 你的房间里。
（语气强烈，表示非常肯定）
It can't be my brother. He is still in France.
不可能是我哥哥，他还在法国呢。（表示不可能）
It could be your brother. He said he might come back.
可能是你哥哥。他说过他可能会回来。（表示猜测可能）
... ... ...
Exercises
1. Complete the sentences with could, must or mustn’t.
keep out意为“留在外面；置身......之外”。
1.It is dangerous. You ______keep out!
2.These stairs are not safe. You _______use them.
3.The rocks are falling down. You _____get hit.
4.The river is too deep. You _______swim in it.
5.Betty _____know what to do , because she did some basic medical training.
2. Underline the correct words to complete the first aid instructions.
1 Get / Do not get medical help immediately.
2 Ask / Do not ask them where the pain is.
3 Lift / Do not lift them because you may drop them.
4 Keep / Do not keep them warm.
... ... ...
by warning them that a tsunami...
by意思是“通过；以（某种方式）”，后面常跟名词，代词，V-ing形式，表示通过某种方式、手段等。提问时用how。
The old man makes his living by selling newspapers.
by的其他几种用法：
1、表示方位“在......旁边”。He sat down by the door.
2、表示时间“在......之前”。Can you finish the work by 5 o'clock.
3、表示交通方式“搭乘”。I go to school by bike.
4、by固定搭配。by the way顺便说一下 by oneself独自一人
... ... ...
（中考链接）
Parents enjoy any progress their children have made and will feel____them.
A. angry with B. interested in
C. proud of D. worried about
Work in groups. Choose an accident from the list in Activity 8 and give instructions about what to do.
When there is School accident…
First…
Second…
Third…
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