It was late at night and Joe .....(still study) for his test.
It was late at night and Joe was still studying for his test
Mary .....(LISTEN) to music when the door bell ...(ring) for the first time.
Mary WAS LISTENING to music when the door bell RANG for the 1st time.
We'll go on the next train. When we .....(arrive) at the station, the 9 o´clock train ....(leave) 10 minutes before.
We'll go on the next train. When we ARRIVED at the station, the 9 o'clock train HAD LEFT 10 minutes before.