Chuyển câu cho nghĩa không đổi

1. The explorer is Christopher Columbus. He discovered America
 - The explorer who.....
2. The weather forecast says it will be sunny tomorrow. My grandma is watching it.
 - The weather forecast which....
3. The man is talking to Jack over there. He is my new English teacher.
 - The man who is....
4. We know a lot of people. They live in Ho Chi Minh City
 - We know....