1.My father waters this flower every morning.

=> this flower is watered by my father every morning

2.John invited Fiona to his birthday party last night.

=> Fiona was invited to John's birthday party last night

3.Her mother is preparing the dinner in the kitchen.

=> The dinner is being prepared in the kitchen by her mother

4.We should clean our teeth twice a day.

=>Our teeth should be cleaned twice a day

5.Our teachers have explained the English grammar.

The english grammar has been explained by our teachers

6.Some drunk drivers caused the accident in this city.

=> The accident was caused by some drunk drivers in this city

7.Tom will visit his parents next month.

=> Tom's parents will be visited next month

8.The manager didn’t phone the secretary this morning.

=> the secretary wasn't phoned by the manager this morning

9.Did Mary make this beautiful dress?

Was this beautiful dress made by Mary?

10.I won’t hang these old pictures in the living room.

=> These old pictures won't be hung in the living room

11.The German didn’t build this factory during the Second World War.

=> This factory wasn't built by the german during the second world war

12.The Greens are going to paint this house and these cars for Christmas Day.

=>This house and these cars are going to be painted by the greeens for christmas day

13.Ann had fed the cats before she went to the cinema.

=> the cats had been fed by Ann before she went to the cinema

14.The students have discussed the pollution problems since last week.

=> the pollution problems have been discussed by the students since last week

15.Have the thieves stolen the most valuable painting in the national museum?

=> has the most valuable paiting in the national museum been stolen by the thieves?