When should you use the imperfect progressive in Spanish?

(1 point)
Responses

to express any action in the past
to express any action in the past

to express completed actions in the past
to express completed actions in the past

to express an ongoing action in the past that is interrupted
to express an ongoing action in the past that is interrupted

to express an action that will be interrupted in the future
to express an action that will be interrupted in the future

The correct answer is: to express an ongoing action in the past that is interrupted.