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 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. Some even die 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 dialect differences. Chinese has been spoken for thousands of years by millions of speakers. Their differences between the dialects of Chinese are so great that speakers of Chinese from some parts of China cannot understand speakers from other parts.
The first paragraph mainly tells us that ______.
A.most people in the world speak Chinese
B.there are thousands of languages in the world today
C.man has much knowledge about languages
D.some people know several languages
第2题
A.正弦交变量在一周期中出现的最大平均值叫做交变量的最大值
B.正弦交变量在一周期中出现的最大瞬时值叫做交变量的最大值
C.正弦交变量在两个周期中出现的最大瞬时值叫做交变量的最大值
D.正弦交变量的最大值,也称峰值或振幅
第4题
正弦交流电平均值是指:正弦交流电在()周期内所有瞬时值的平均值。
A.正半
B.负半
C.一个
D.波形
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