1. Whose friends, John and lily are going to plant trees next weekend?(对my提问）
2. Which of your friends are going to plant trees next weekend?(对John and lily提问）
3. What are your friends, John and lily going to do next weekend?(对plant trees提问）
4. When will your friends, John and lily go to plant trees next weekend?(对next weekend提问)
希望能帮到你:)