What were you doing when the alarm rang? Why are you spinning a basketball?
It rang while I was playing basketball. / I was playing basketball when it rang.
What were you doing when the alarm rang? Why are you holding a broom?
I was sweeping the floor when it rang. / It rang while I was sweeping the floor.
What were you doing when the alarm rang? Why are you wearing?
It rang while I was listening to the music. / I was listening to the music when it rang.