1.Wood is used to make paper by us.
2.He was heard to sing in the music room by me.
3.Your exercise book must be handed before class.
4.A large number of people in the world speak Chinese.
5 When were they invented
6.Who was the inventor of the alarm clock
或：By whom was the alarm clock invented
不明白的再问哟,请及时采纳,多谢!