Throughout history, people have been interested in knowing how languages first began, but no one knows exactly where or how this happened. However, we do know a lot about languages, the languages of today and also the languages of earlier times. There are probably about 3,000 languages in the world today. Chinese is the language with the most speakers. English, Russian and Spanish are also spoken by many millions of people. On the other hand, some languages in the world have less than one hundred speakers.
There are several important families of languages in the world. For example, most of the languages of Europe are in one large family called Indo-European. The original (最初的) language of this family was spoken about 4,500 years ago. Many of the present day languages of Europe and India are modern forms of the language of 4,500 yeas ago.
Languages are always changing. The English of today is very different from the English of 500 years ago. In time some even died out completely. About 1,000 years ago, English was a little-known relative of German spoken on one of the borders of Europe.
If a language has a large number of speakers or if it is very old, there may be differences in the way it is spoken in different areas. That is, the language may have several dialects. Chinese is a good example of
既无最小值也无最大值；
上随机取一个数
，使得
成立的概率为
；
对任意正实数
恒成立，则正实数
的最小值为16；
，若方程
恰有三个不同的实根，则实数
的取值范围是
；以上正确的命题序号是： .
