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.