which side are you on?

题目

which side are you on?
which side are you on
which side do you on?
哪个对,为什么?

答案

which side are you on 是对的.
你在哪一边?
which side do you on?是错的,因为这个句子如果是个陈述句,没有实义动词,所以不能用do.