I am a Chinese teacher. (一般现在时态)。
I am not a Chinese teacher.
He was from Canada. （一般过去时态）。
He was not from Canada.
Linda is playing the piano. (一般现在时态)。
Linda is not playing the piano.
The Greens were going to Taiyuan to visit their grandpa tomorrow. (过去将来时态)。
The Greens were not going to Taiyuan to visit their grandpa tomorrow.
They are watched in the jail. (现在时态的被动语态)。
They are watched in the jail.
总结：含有be动词的句子，在变否定句是，不论任何时态和语态，只要在含有be动词后加否定词not 即可。其中除了am not 不能进行缩写之外，剩余的含有be动词和not 都可以进行缩写。
I am a doctor. (一般现在时态)。
-Are you a doctor?
-Yes, I am. / No, I am not.
Her mother was cleaning the bedroom. （过去进行时）。
-Was her mother cleaning the bedroom?
-Yes, she was. / No, she wasn’t.
They are going to the Summer Palace next weekend. (一般将来时态)。
-Are they going to the Summer Palace next weekend？
-Yes, they are. / No, they aren’t.
The flowers were watered by them carefully everyday last year. (过去时态的被动语态)。
-Are the flowers watered by them carefully everyday last year?
-Yes, they were. / No, they weren’t.
三． 含有be动词的句子直接引语变间接引语时要将含有be动词用if 或whether替换。
She asked, “ Is your sister a popular singer?”
She asked that if / whether my sister a popular singer?
Jim askes, “ Are you her brother?”
Jim askes that if /whether I am her brother?