He was at the police station yesterday.（改为一般疑问句）顺便教一下怎么改疑问句,

1) Was he at the police station yesterday?
一般来说改疑问句分两种情况：
1）一般疑问句
有be动词的，将be动词提到句首。没有be动词的，用助动词来提问，助动词也在句首。
eg . I am a student. Are you a student?
I like apples. Do you like apples?
2）特殊疑问句
特殊疑问句要用疑问词（比如：what，when，how等）来提问。有be动词的句子：”疑问词+be动词 来提问“，没有be动词的：”疑问词+助动词“来提问。
eg. My name is Mike. What's your name?
I bought it at the supermarket. Where did you buy it?

Was he at the police station yesterday?
一般疑问句是用yes和no回答的,改法：将陈述句中的be动词，情态动词（can,may,should等）或助动词（do,does,did,have,has等）提前。如：
she is a teacher改为：is she a teacher?
she can sing. 改为：can she sing?
she likes apples.改为：Does she like apples?
特殊疑问句改法（一般以对划线部分提问的形式出现）：
1.特殊疑问词+一般疑问句（去掉划线答案）例如：she likes apples改为：what does she like?
2.如果提问主语，将主语用特殊疑问词替掉，后面句子不变。如Mary is beautifu.改为：who is beautiful?

Was he at the police station yesterday?
1、谓语动词是be动词、助动词、情态动词时,只要直接把这些词置于句首,句末改成问号.2、谓语动词是行为动词时,必须在句首加上助动词Do、Does（三单）、Did（过去式）加上这些助动词后,句子中谓语动词必须用原形,句末改成问号.

Was he at the police station yesterday?一般陈述句改为疑问句，都是将助动词提前