EX 3:
1. When I arrived, Jack had left the office
2. While I was having lunch, someone rang the bell
3. The last time I went to the dentist was 6 months ago
4. She began studying Japanese was 5 years ago
5. After he had done all his work, he went home
6. Before Steven bought a new mortorbike, he had saved enough money
7. When we tidied the house, the guests had heft
8. It's ages since the last time we heard them
9. Please remember to buy some stamps
10. Sheila forget to phone Peter
11. We regretted selling our house