M3 Unit 1 Festivals around the World

Section VI Grammar -Modal Verbs

学习目标：掌握情态动词的基本含义和用法。

学习过程

语法知识-预习探究

一 我的观察

下文是学校的一些规定，你能搞清楚，哪些事可以做，哪些事不能做吗？

Students mustn't leave the campus at school hours, so we have to have lunch at school. However, we don't have to bring your lunch-boxes because we have a dining hall inside the school. We ought to be tidy and orderly there, but luckily for us, we needn't wash up after dinner.

二 我的发现:

请你写出我们本单元要学习的情态动词的汉语意思。

ought to ought not to have to don't have to mustn't needn't

三 我的讲解

1. must和mustn't

1）must表示"必须"，是一种语气很强的要求。否定式must not(mustn't)表示 "不准","禁止"等。在回答带有must的问句时，否定式常用need not(needn't)或don't have to 表示"不必"，而不用must not (mustn't)。

-Must I be home before eight o'clock?

-Yes, you must./No, you needn't./No, you don't have to.

2）must表推测，

①一般只用于肯定句中，表示"一定"，"必定"。

You must be very tired after such a long walk.

②表示对过去事情的推测，用"must+完成时"。

You must have left your umbrella in the theatre.

③当must表推测之意时，其否定形式常用can not而不用must not。

His car is still here. He can't have left

④ 如果表示对正在发生的动作的推测，就用"must+进行时"。

Dad is always an early bird. He must be taking his usual morning exercise in the park now.