`1` The watch was bought at the shop.

`=>` Câu bị động quá khứ đơn

`(+)` S + was / were + Vpp + by O.

`2`  The house was built in `1950`.

`=>` Câu bị động quá khứ đơn

`(+)` S + was / were + Vpp + by O.

`3` The exercisess were done last week.

`=>` Câu bị động quá khứ đơn

`(+)` S + was / were + Vpp + by O.

`4` The letters were sent the day before yesterday.

`=>` Câu bị động quá khứ đơn

`(+)` S + was / were + Vpp + by O.

`5` The lesson was learnt by him `2` weeks ago.  

`=>` Câu bị động quá khứ đơn

`(+)` S + was / were + Vpp + by O.

`6` Kieu story was writen by Nguyen Du.

`=>` Câu bị động quá khứ đơn

`(+)` S + was / were + Vpp + by O.

`7` The cake was made last night.

`=>` Câu bị động quá khứ đơn

`(+)` S + was / were + Vpp + by O.

Câu bị động QKĐ :

` -> ` : S + was / were + VPII + by + O

DHNB 

` + `  ) Last night

` + `  )  Yesterday

` + `  ) last week

` + `  ) ...

` 1 ` : The watch was bought at the shop

` 2 `  : The house was built in 1950

` 3 `  : The exercises were done last week

` 4 ` : The letters were sent the day before yesterday

` 5 `  : The lesson was learnt by him 2 weeks ago

` 6 `  : Kieu story was written by Nguyen Du

` 7 `  : The cake was made last night