Công thức thì QKTD 

(+) S + was/were + Ving 

(-) S + was/were+ not + Ving 

(?) Was/Were +S +Ving? 

--> Diễn tả hành động đang xảy ra ở 1 thời điểm nào đó trong quá khứ 

--> Diễn tả hành động đang xảy ra thì có hành động khác chen vào (while / when)

DHNB: at + giờ + thời gian trong QK, at this time + thời gian trong QK, …

Công thức thì QKĐ (V: to be)

(+) S + was/were + ... 

(-) S + was/were + not ... 

(?) Was/Were + S ... ? 

S số ít, I, he, she, it + was

S số nhiều, you, we ,they + were

Công thức thì QKĐ (V: thường)

(+) S + V2/ed 

(-) S + didn't + V1 

(?) Did + S+ V1?

DHNB: ago, last (year, month ...), yesterday, in + năm QK, ...

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7. was walking / met

8. were you speaking / came 

9. was reading / heard 

10. rescued / was 

11. opened / were standing

12. was arrived / were having

13. did / saw 

14. asked / was looking

15. weren’t driving / stopped

16. was driving / had 

17. had / did

18. were hiding / came

19. planned / phoned

20. were cleaning / broke

21. was looking / saw 

`color{orange}{~LeAiFuRuiHuiBao~}`