最简单的：
Jack is a teacher in the school.
如果划线部分为 Jack,jack是一个人名 所以要用who来提问
就是：who is a teacher in the school?
如果划线部分是 a teacher ,a teacher是一份职业,就要用what job来提问
就是：what's Jack's job in the school?
否定句形式：在是动词或者助动词后面加not就可以了.
Jack is not a teacher in the school.
is am are do does did done等都是是动词或者助动词