1. I visited the school in which / where I had studied;
2. He is the man that / who / whom / - I am looking for.
3. I received the letter that / which / - my uncle posted;
4. Her boy friend is a person who tries to make her happy;
5. I still remember the things that / which happened in the school;
6. The most important thing that we need to consider is who will give the lecture;
7. A man who is called Mr. Green wants to see you.