阅读下面短文，按照句子结构和上下文连贯的要求，在空格处填入一个适当的词或使用括号中单词的正确形式填空。

There's one language that people use in every country. People, young old, short and tall, use it very often. It's (everybody) second language-sign（手势）language.

you wave your hand in the street, you are saying "hello"to your friend. When you put up your hand in class, you are (tell)the teacher that you know the answer. When a policeman (want) to stop cars or buses in the street, he raises his hand. All of (they) are using sign language. In some (place), you have to use sign language to talk with others. For example, when you are swimming your friends, you can have a talk under water by(use) sign language. an interesting language!