1. He's the teacher who helped me to pass the exam. (Относится к человеку).
2. That's the school where I went when I was five. (Относится к месту).
3. Do you remember the time when I fell into the river? (Относится ко времени).
4. She's the girl whose father is an actor. (Принадлежность).
5. Have you read the essay that/which I wrote? (Относится к предмету, можно использовать 'that' или 'which').
6. This is the email that/which came yesterday. (Относится к предмету, можно использовать 'that' или 'which').
Ответ: 1. who; 2. where; 3. when; 4. whose; 5. that/which; 6. that/which.