根据短文理解，用括号所给单词的正确形式填空。

      People ____ （live） in different countries made different kinds of languages. Today there are about fifteen hundred ____ in the world. Each contains many thousands of words. A very large dictionary, for example, contains four ____ five hundred thousand words. But we do not need ____ these. To read short stories you need to know only about two thousand words. ____ you leave school, you will learn only one thousand or more.

      The words you know are called your vocabulary. You should try to make your vocabulary ____ （big）. Read as many books as we can. There are a lot of books ____ （write） in easy English. You will enjoy them. When you meet ____ new word, look it ____ in your dictionary. Your dictionary is your ____ （much） useful book.