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, ...

-----------------------------------------------------

1. rang / was having 

2. were wearing / met 

3. rained / was carrying 

4. were playing / was writing 

5. was / had thought 

QKHT: S + had+ V3/ed 

6. mentioned / had never heard 

Before + QKD, QKHT

7. went / were playing / said / had been playing 

DHNB: since (QKTD)

S + has/have + been + Ving 

8. was singing / came 

9. asked / had happened 

10. was eating / went 

`color{orange}{~MiaMB~}`