請依下文回答第 36 題至第 40 題：
The speech of every group of people has developed differently. One reason for this is that each group often lived in isolation. Another reason is that each language grew up 36___ under different conditions. Gradually, over many centuries, some groups came in contact with other groups. When this happened, their languages grew more and more
37____ . In other cases, however, a group would break apart, and new languages would grow from the original one. The
new languages, though distinct in many ways, would 38_____ similarities to one another.
There are many different countries in the world today. One might conclude that each country has its own language and that languages are only as numerous as countries. Actually, there are many more languages than there are countries. 39____ , in the United States, we have considered English the one language of the people. Yet at one time, on the Great Plains alone, more than 22 native American languages were spoken.
In addition, a single language may have two or more dialects, or varieties. 40_____ is estimated that there are several thousand languages and dialects spoken in the world today.