句型转换。 1. John answered all the questions. (改为被动语态) All the questions _____ _ _____ John. 2. They are too tired to continue working. (改为同义句) They are _____ _____ _____  they can't continue working. 3. His brother joined the army when he was 22. (改为同义句) His brother joined the army _____ _____ _____ _____ 22. 4. What a tall tree this is! (用how改写) _____ _____ _____ tree this is! 5. Some people believe that Chinese is difficult to learn. (改为同义句) It _____ _____ _____ Chinese is difficult to learn.