2016-2017学年 人教版 必修三 Unit 2 Healthy eating learning about language 课件 (4)
2016-2017学年 人教版 必修三  Unit 2 Healthy eating learning about language 课件 (4)第4页

There will be an exam about modal verbs, so we have to master the grammar.

  — Must I master the usage of modal verbs ?

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

(necessity)