Past Continuous:
•I was watching TV when she called.
•When the phone rang, she was writing a letter.
•While we were having the picnic, it started to rain.
•What were you doing when the earthquake started?
•I was listening to my iPod, so I didn't hear the fire alarm.
Present Continuous:
•You are learning English now.
•You are not swimming now.
•Are you sleeping?
•I am sitting.
•I am not standing.