Răspuns:
1.Alex and Sue were watching a film on DVD when their friends arrived.
While Alex and Sue were watching... their friends arrived.
2.Marco was having breakfast when he had a great idea.
While Marco was having breakfast he had a great idea.
3.Cristina was talking on the phone when her father went out.
While Cristina was talking on the phone her father went out.
4.They were walking in the mountains when they saw a strange bird.
While they were walking in the mountains they saw a strange bird.
