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: 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. I was shopping when Linda called me.

2. My brother was doing his homework at 9 o'clock.

3. He was eating lunch when we arrived.

4. Was she living in Hue at that time?

5. Was she playing the guitar at 6 p.m?

6. Was she typing a letter when her boss went into the meeting room?

7. While she was watching TV, she heard the doorbell.

`color{orange}{~MiaMB~}`