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, ...

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

2. I was choosing a bracelet for Mum when Mum came into the shop.

3. Louise was talking to Amy when the bus arrived.

4. When Harriet was looking for some plasters, she found her watch.

5. The team was training when Ted had an accident.

6. When we were walking around the ruins, some stones fell.

7. The actor was performing on stage when the director started to laugh.

8. When I was carrying some bottles, the carrier bag broke.

9. When they were shopping, it started to rain.

`color{orange}{~MiaMB~}`

$#AP$

I was choosing a bracelet for Mum when Mum came into the shop

Louise was talking to Amy when the bus arrived

When Harriet was looking for some plasters, she found he watch

The team was training when Ted had an accident

When we were walking around the ruins, some stones fell

The actor was performing on stage when the director started to laugh

When I was carrying some bottles, the carrier bag broke

When they were shoping, it started to rain

`@` QKĐ:

`-` S + were/was

    S + V_past form

    S + weren't/wasn't

    Was/were + S?

    Did + S + V-inf

`@` QKTD:

`-` I/he/she/It + was + V_ing

    I/he/she/It + wasn't + V_ing

    Was + he/she/it + V_ing

    Were + you/we/they + V_ing