＃ be动词的否定 在`am,is,are,was,were`后面加`not`. 缩略式 `am not,isn't,aren't,wasn't,weren't` ``` The man isn't back.那个男人没回来。 I am not back. They aren't back. He wasn't back. They weren't back. ``` # be动词提问和回答 疑问句，将be动词提到句子最前面 - Is he a teacher?(he is a teacher.) Yes,he is./No,he isn't. - Are you a teacher?(you are a teacher.) Yes,I am./No,I am not. - Were they teachers? Yes,they were./No,they weren't. ``` They weren't in the classroom yesterday. 他们昨天不在教室。 ```