1.WhenI came into the classroom the pupils were discussingthe plan of excursion.They had been already discussingitfor 20minutes.
2.When Olga finished the university her sisterhad been teaching English at school for 5 years
3.Hisparents leftthe apartmentwherethey had been living for20 years.
4.I was looking for mycopybook for half an hourbefore I had been finding it underthe newspaper.
5.When we left home it was raining. It had beenalready raining fortwo hours.