8, this Math problem was solved by my daughter in five minutes

9, The ao dai was mentioned in these songs by some musicians a long time ago

10, All the schools were improved in district two years ago

11, A lot of trees were planted around the school

12, The classroom was cleaned carefully yesterday

`8.`This Math problem was solved by my daughter in five minutes.

`9.`The ao dai was mentioned in these songs by some musicians a long time ago.

`10.`All the schools were improved in the district two years ago.

`11.`A lot of trees were planted around the school.

`12.`The classroom was cleaned carefully yesterday.

`=>`Cấu trúc câu bị động với thì quá khứ đơn :

`(+)` Khẳng định : S + was/were + Vpp + (by O)

`(-)` Phủ định : S + was/were not + Vpp + (by O)

`(?)` Câu hỏi nghi vấn : Was/Were + S + Vpp + (by O) ?

* Notes :

`-`Với các chủ ngữ chủ động là "I, he, she, we, they" thì khi viết lại với câu bị động, ta có thể lược bỏ phần "by O"

`-`Với các chủ ngữ chủ động là "People, noone, someone, nobody,...." thì khi chuyển sang câu bị động, ta phải lược bỏ phần "by O"