Mengubah active menjadi passive

1) Somebody had cleaned the room.
# The room had been cleaned by somebody.
2) They have postpone the meeting.
# The meeting have been postpone by them.
3) Somebody is using this computer.
# This computer is being used by somebody.
4) I didn't realize that somebody was recording our conversation.
# I didn't realize that our conversation was being recording by somebody.
5) They are building a new ring road.
# A new ring road are built by them.
6) They have built a new hospital.
# A new hospital has been built by them.
7) Somebody stole my bag.
# My bag was stolen by somebody.
8) She made this cake.
# This cake was made by her.
9) She is teaching this class.
# This class is being teached by her.
10) Has a dog ever bitten you?
# Have you ever bitten by a dog?