1.they had postponed the flight because of the bad weather before yesterday

The flight had been postponed because of the bad weather before yesterday

2.our teachers have explained the English grammar

The English grammar have been explained by our teachers

3 that factory is producing more and more pollution

More and more pollution is being produced by that factory

4. A child can understand the problem

The problem can be understood by a child

5 i feed my cat twice a day

My cat was fed by me twice a day

6.my mother is preparing a big dinner

A big dinner is being prepared by my mother

7. Nobody can defeat him

He can't be defeated 

8. People will destroy the old building at the end of the street

The old building at the end of the street will be destroyed 

9.i had finished these tasks before my boss came back from his trip

These tasks had been finished by me before my boss came back from his trip

NHỚ VOTE 5 SAO VÀ CTLHN CHO MIK NHÉ. THANKs!!!

1. The flight had been postponed because of the bad weather before yesterday

2. The English grammar have been explained by our teachers

3. More and more pollution is being produced by that factory

4. The problem can be  understanded by a child

5. My cat is feeded by me twice a day

6.  A big dinner is being prepared by my mother

7. He can't  be defeated

8. The old building will be destroyed at the end of the street

9. These tasks had been finished by me before my boss came back from his trip