giải giúp em với mn ơi

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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1. opened / was raining

2. was studying/ suddenly felt

3. were listening / phoned

4. was having / rang

5. was going / started

6. went / was reading

7. Were you thinking / called

8. were waiting / arrived

9. was climbing / began

10. was driving / saw 

11. was reading / went

12. began / was cycling

13. woke / was

14. was walking / heard

15. were playing / came

16. left / was still shining

17. ran / was walking

18. were you doing / rang

19. were having / arrived

20. came / was sleeping

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