The past perfect:
1. Yesterday they went home after they ( finish) their work.
2. When we came to the stadium, the match already ( start).
3. many people ( move) to the new place before the storm occurred.
4. I sat down and rested after they ( go).
5. Before he died, he (be) ill for several days.
6. Last night before he watched TV, he ( do) the exercise.
7. Ba went to the department after she ( clean) the floor.
8. When I got to the party, they ( go) home.
9. By the time the police arrived, the house ( be) burned down.
10. By last year, twenty schools in this province ( be) build).