=>
1. This flower is watered by my father every morning.
-> bị động HTĐ is/am/are V3/ed
2. Fiona was invented by John last night.
-> bị động QKĐ was/were V3/ed
3. The dinner is being prepared in the kitchen by her mother.
-> bị động HTTD is/am/are being V3/ed
4. Our teeth should be cleaned twice a day.
-> bị động should be V3/ed
5. The English grammar has been explained by our teachers.
-> bị động HTHT have/has been V3/ed
6. The accident was caused in this city by drivers.
-> bị động QKĐ was/were V3/ed 
7. Tom's parents will be visited by him next month.
-> bị động TLĐ will be V3/ed
8. The secretary wasn't phoned by the manager this morning.
-> bị động QKĐ was/were (not) V3/ed
9. Was this beautiful dress bought by Mary?
-> bị động QKĐ was/were S V3/ed?
10. These old pictures won't be hung in the living room.
-> bị động TLĐ will (not) be V3/ed
11. This factory wasn't built by the German during the Second World War.
-> bị động QKĐ was/were (not) V3/ed
12. This house and these cars are going to be painted for Christmas Day by the Greens.
-> bị động is/am/are going to be V3/ed
13. The cats had been fed by Ann before she went to the cinema.
-> bị động QKHT had been V3/ed
14. The pollution problems have been discussed by the students since last week.
-> bị động HTHT have/has been V3/ed
15. Has the most valuable painting in the national museum been stolen by the thieves?
-> bị động HTHT have/has S been V3/ed?