1. Candidates may not use the dictionaries (BY)
- The dictionaries may be used by candidates.

2. People said that the President was killed by a mad man (IT)

- It was said that the President was killed by a mad man.

3. I didn’t realize that someone was recording our conversation (BEING)

- I didn’t realize that our conversation was being recorded.

4. They asked me some difficult questions at the interview (I)

- I was asked some difficult questions at the interview.