かれはまどをあけますか。How to convert it to “Why did he open the window?”


I am a beginner Nihongo learner. I know Did he open the window? -
かれはまどをあけますか。I just don't know where to insert the "why" in the sentence.
Actually, I was a little disappointed that this question is put on hold,
thinking that people here is not that helpful to people like me.

