Past continuous for actions in progress at a specific point in the past

The past continuous tense is used to refer to actions that were in progress at or around a specific point in time in the past. This point can be implied or expressed with a time expression or a clause with a verb in the past simple tense:

At 9 o'clock, I was sitting on the train.
A few minutes ago, they were still dancing.
When I called her, she was studying.
What were you doing when you heard the explosion?
Sorry, can you repeat that? I wasn't listening. (when you said that)