they missed the train (because the clock was ten minutes slow).(对划线部分提问）
问题描述：
they missed the train (because the clock was ten minutes slow).(对划线部分提问）
答
Why did they miss the train?
答
对because引导的原因状语从句提问用疑问词why
即Why did they miss the train?
答
划线部分是原因 用why 提问 过去时态 助动词用did体现 动词变为原型miss,其他照抄
答案：Why did they miss the train?