1. You are imitating the other people, right?
2. That letter was written by David.
3. The hotel over there is being built by them.
4. The books will be packed and posted by Tom.
5. A man such as he should never be forgotten by the people.
6. Nothing was being done about it by them.
7. I told you about the job, did you get any offers?
Explanation: The active voice is basically "subject + infinitive + object," so when the sentence is placed in a different form then this, you get the passive voice.