Question

she was a doctor改为否定句

Answer 1

She was not a doctor.
解析：此句含有系动词was，所以否定句直接在系动词后面加上not即可。
补充：如果句子里没有系动词，有情态动词，则在情态动词后面加上not，如果都没有则借助于助动词do/does/did。

Answer 2

she was a doctor改为否定句
She wan't a doctor.
她不是一名医生。

Answer 3

你好！
she was a doctor改为否定句
she was not a doctor

Answer 4

这个句子有问题吧。
she is a doctor
否 she is not a doctor
she was a doctor last year（有过去时间就行）
she was not a doctor

Answer 5

she wasn't a doctor.