---Someone is knocking at the door. Who may it be? ---It ______ be Tom. He is still in the school.
— My father has just bought a new computer. — Really? How lucky are!
Uncle Wang taught Jim how the washing machine.
Patrick is interested in animals, so he enjoys _ every Saturday working in an animal hospital.
Peter’s parents were worried that Peter too much time on line.
Beijing ,the capital of China, is one of cities in the world.