用be动词造一句话改为否定句、疑问句

肯定句: She is a doctor.

否定句: She isn't a doctor.

疑问句: Is she a doctor？

肯定回答: Yes, she is.

否定回答: No, she isn't.

希望这些例子能帮助你理解be动词在不同句型中的用法。