【往期回顾】
下面是第123-124课的参考答案：
1. That is our English teacher who plays football very well.
That is our English teacher playing football very well.
2. This is the book which has been translated into many foreign languages.
This is the book having been translated into many foreign languages.
3. Have you watched the game which was held in Shanghai yesterday?
Have you watched the game held in Shanghai yesterday?
4. The soldier who has saved ten children from the fire is only nineteen years old.
The soldier having saved ten children from the fire is only nineteen years old.
5. Do you know the man who is keen on extreme sports?
Do you know the man keen on extreme sports?
一、课文原文
本课学习的是情态动词must、need和have to的用法。
（一）must
本课的must表“必须”，其基本用法为：
sb. must do sth.
如：
I must go there at once.
其否定表达为：
sb. needn't / don't have to do sth.
如：
I needn't / don't have to go there at once.
【注意】
needn't与mustn't的区别：
needn't表示“不必”，mustn't 表示“禁止；不能”。如：
He needn't do it now.
他不必现在就做。
He mustn't do it now.
他不能现在就做。
其疑问句的表达为：
must sb. do sth.
如：
Must you go there at once?
What must you do at once?
（二）need
need用作情态动词，表示“需要；必须”，但一般用于否定句中，作为must的否定表达，其基本用法为：
sb. needn't do sth.
如：
She needn't buy a house of her own.
【注意】
need作为情态动词，一般不用于肯定句，但偶尔也会用于疑问句，如：
Need she leave now?
need还可以用作实意动词时，其基本用法为：
sb. need sth. sb. need to do sth.
如：
She needs some help from us. She does not need to get up early tomorrow.
need也可以用作名词，如：
They are in great need of medicine.
（三）have to
have to其实不是情态动词，只是表示“必须；不得不”，其语法变形都按照实意动词的要求进行变化，基本用法为：
sb. have to do sth.
如：
She has to buy more ink.
其否定表达为：
sb. don't have to do sth.
如：
She doesn't have to buy more ink.
其疑问句的表达为：
do / does sb. have to do sth.
如：
Does she have to buy more ink? What does she have to buy?
【注意】
don't need to do和don't have to do可以互换使用。
三、一课一题
根据本课的重要语法点，让我们来练一练吧，按要求改写下列句子。
1. She must drink some water immediately. (改为否定句)
2. He needs to do his homework every day. (改为否定句)
3. I have to lend him my notebook. (对划线部分提问)
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