1. had not used
2. hadn't studied
3. destroyed
4. had already done
5. hadn't ordered
6. Had you given
7. took
8. had left
9. had washed
10. went
11. had met
12. ate
13. came
14. started
15. had fed
Nếu trong quá khứ có 2 hành động, QKHT dùng để nhấn mạnh hành động xảy ra trước, QKĐ để diễn tả hành động xảy ra sau (dấu hiệu nhận biết kiểu câu này: before, after)
