Answer:
1) Those skyscrapers were built by a well-known architect.
2) A new scooter will be bought by Susan.
3) My room was redecorated by me.
4) The color had been chosen by Mr. Radisson.
5) Was the taxi stopped by Mum.
6) I can't be woken up by the alarm clock.
7) A lot of meat is eaten by the people in Serbia
8) Is the fruit frozen by them?
1)was pulled
2) was lost
3) should be discussed
4) Our offer shall be accepted
5)aren't held
6) was written
7) must not be arrested
8) The mail is delivered
Explanation:
In an active sentence, the subject is doing the work. While in a passive sentence, the work is done by the subject.