英语肯定句疑问句否定句的转换请用一句英语

问题描述:

英语肯定句疑问句否定句的转换请用一句英语
最好用一句话 来转换!说话算话

肯定句 He is a teacher.
疑问句 Is he a teacher?
否定句 He isn't a teacher.