Мне ! надо! преобразовать в пассивный залог. 1 the gardener has planted some trees. 2 someone has broken the vase 3 they have bought a new car recently. 4 she has read many books on astronomy and so she really knows the subject. 5 nobody has discovered a cure for the common cold yet.

1. Some trees have been planted by the gardener.
2. The vase has been broken by someone.
3. A new car has been bought by them recently.
4. Many books on astronomy have been read by her so the subject is really known by her.
5. A cure for the common cold has been discovered by nobody yet.

1 some trees have been planted 
2 the vase has been broken
3 a new car has been bought recently
4 many books on astronomy have been read by her and so the subject is known
5 A cure for the common cold has not been discovered yet