used to do否定句疑问句讲解used to do sth.句型表示“过去常常,过去习惯.”表示过去的某种习惯(过去经

否定句 主语+didn't use to+动词原形
一般疑问句 Did + 主语+use to+动词原形
特殊疑问句 特殊疑问词+ did + 主语+use to+动词原形
He used to go to school on foot.
否定句 He didn't use to go to school on foot.
一般疑问句 Did he use to go to school on foot?
特殊疑问句 How did he use to go to school