27. A merica was discovered by Christopher Columbus.

28. We were given a lot of presents by The teacher.

29. She was to made run away.

30. He was made to study hard for the exam by his parents.

31. The ao dai in poems has been mentioned by poets.               

=> Câu bị động:

- thì Quá khứ đơn: S + was/were + Ved/V3 + (BY  O)

- thì Hiện tại hoàn thành: S + have/has + been + Ved/V3 + (BY  O)

`27.` America was discovered by Christopher Columbus

`-` Thì QKD(Passive): S + was`/`were + `V3` (+ by sb`/`O)

`28.` We was given a lot of presents by the teacher

`29.` She was made to run away

`-` Make(Passive): S + be + made to V... (+by sb`/`O): bị bắt làm gì

`30.` He was made to study hard for the exam by his parents

`31.` The ao dai in poems has been mentioned by poets

`-` Thì HTHT(Passive): S + have`/`has + been + `V3` (+ by sb`/`O)