11. The Browns (do) were doing their housework when you (come) came last Sunday.

12. I (see) saw a car accident while I (wait) was waiting for you on this corner yesterday.

13. What was you doing (do) when she (phone) phoned last Monday?

14. I (walk) was walking in the street when I suddenly fell over.

15. She (play) was playing the piano when our guests (arrive) arrived last night.

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$Form:$

$-$ Thì quá khứ tiếp diễn + WHEN +thì quá khứ đơn.

$-$ Thì quá khứ đơn + WHILE + thì quá khứ tiếp diễn.

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$@haanx2$

`-` Thì QKĐ : S + Ved / V2

`=>` `DHNB` : yesterday , ago , last , ...

`-` Thì QKTD : S + was / were + V-ing

`=>` `DHNB` : this time yesterday , at this time yesterday , ...

`11`.were doing / came

`12`.saw / was waiting

`13`.were ... doing ? / phoned

`14`.was walking

`15`.was playing / arrived

`\text{# TF}`