??People often use sign （手势）language. It's very important. It's easy to understand. When you wave（向……挥手）to a friend in the street, you are using sign language. When the teacher asks you some questions in class, you put up your hand, you are saying, " I think I can answer the question." When policemen want to stop cars and buses in the street, they're using sign language. Sign language is very helpful. Even when you are swimming with your friends, you can talk with them under water.

根据短文内容，选择最恰当的答案。

　　1. It's very important for us to ________.

[??]

　　 A. use language???????B. use sign language

　　 C. use foreign language???D. use hand language

　　2. When you see your friend in the street, you wave to him,means:

[??]

　　 A. you speak to him.?????B. you put up your hand.

　　 C. you say hello to him.???D. you say goodbye to him.

　　3. If you can answer teacher's questions, you ______.

[??]

　　 A. put up your hand???? B. stand up and answer

　　 C. ask your teachers????D. use sign language

　　4. Policemen use sign language to ______ in the street.

[??]

　　 A. ask the drivers?????B. let people go

　　 C. stop cars and buses???D. answer some questions

　　5. Sign language is very ________.

[??]

　　 A. lovely and important???? B. funny and helpful

　　 C. helpful and interesting???D. important and helpful