Period Four　Grammar-Modal verbs(Ⅱ)

阅读以下句子，仔细观察黑体部分并补全空格。

1．By now his restaurant ought to be full of people.

2．Does your father need any help?

3．What do we need to take for the picnic?

4．You needn't try to explain.

5．His mother is ill.He has to stay at home to look after her.

6．Something terrible must have happened if Li Chang was not coming to eat in his restaurant as he always did.

1．以上句子中，第1、4、5、6句中的黑体词都是情态动词，而第2、3句中的黑体词是实义动词。

2．以上各句中的情态动词后都接动词原形。其中第6句中must have happened的意思是"一定已经发生了"。

3．上述句子中ought to意为"应该"；need意为"需要"；has to意为"不得不"。

1．ought to的用法

(1)表示责任和义务，意为"应该"，与should同义。

You ought to be more careful when you do some shopping on the Internet.

在网上购物时，你应该更小心些。

考点警示

ought to的否定形式为ought not to/oughtn't to，一般疑问形式是将ought提至句首，其否定答语通常用don't have to或needn't。

①You ought not to make this kind of mistake again.

你不应该再犯这种错误了。

②-Ought he to see the doctor?

-Yes，he ought (to)．/No，he doesn't have to/needn't.

--他该去看医生吗？

--是的，他该去。/不，他不必去。