Be 动词的否定

在is ,  am , are , was , were 后面加not.

缩略式 isn't ,  am not , aren't , wasn't , weren't .

1.The man isn't back.

2.I am not back.

3.They aren't back. 

4.He wasn't back.

5.They weren't back.

使用be动词提问和回答

- Is he a teacher ?

Yes, he is / No, he isn't

- Are you a teacher ?

Yes, I am / No, I am not

- Were they teachers ?

Yes, they were / No, they weren't

Be动词的练习

1.他是医生吗？（doctor）

Is he a doctor ?

Yes, he is  / No，he isn't.

2.他们昨天在教师吗？（yesterday , classroom ）

Were they in the classroom yesterday?

Yes they were. / No, they weren't

3.他们昨天不在教室。

They weren't in the classroom yesterday.