阅读下列短文，短文中有四处空白，短文后方框内有四个句子，请根据短文内容把他们分别放回到文中原来的位置，以恢复文章的原貌。 A. You nod (点头), and people know you are saying yes. B. Books are written to tell you about all great things in the world. C. A smile on your face shows you are happy and friendly. D. Signs on doors tell you how to go in or out. How do people pass on messages? When you write a letter or make a telephone call, your words carry a message. People communicate with words. Do you think you can communicate without words? Tears (泪) in your eyes tell others that you are sad. 1______ When you put up your hand in class, the teacher knows you want to say something or ask questions. You shake your head, and people know you are saying no. 2______ Other things can also give some information. For example, a sign at the bus stop helps you to know which bus to take. A sign on the wall of your school helps you to find the library. ______ There are a lot of signs around you and you receive messages from them all the time. People can communicate in many other ways. An artist can use his pictures to tell about beautiful mountains, about the blue sea and many other things. ______ They also tell about people and their ideas. Books, magazines, TV, radio and movies all help us to communicate with other people. They all help us to know what is going on in the world.