Đổi sang câu bị động
1. I had bought this pen before I went to bed last night
2. Nina had washed the dishes
3. I had written a report
4. Sam had done his exercise by noon
5. They had not finished the report before they had a test
6. We had seen this movie before Nina called
7. After I had cleaned the house, I went to school
8. After Mark had washed his clothes, he studied
9. Vicky had ironed the clothes by noon
10. I hadn't brushed my teeth before I went to bed last night