Ответ:
- Who has written to her?
- What frightened him?
- What fell on my head?
- Who is talking on the phone?
- Who has stolen her bag?
- What is in the garden?
- Who will bring the parcel?
- Who sent Linda flowers?
- What is making a funny noise?
- Who bought his painting?
если "somebody", то "who"
если "something", то "what"