1. were studying (diễn tả hành động đang xảy ra trong QK thì hành động khác xen vào)
2. was snowing
3. was showing
4. was watching/ was reading (While+S+QKTD, S+QKTD)
5. was waiting (có thời điểm cụ thể trong quá khứ "at 7 pm yesterday" nên chia thì QKTD)
6. Was/working ((có thời điểm cụ thể trong quá khứ)
7. was teaching
8. was blowing
9. was going
10. was visiting