Some things we know about language

    Many things about language are a mystery, and many will always remain so．But some things we do know．

    First, we know that all human beings have a language of some sort．There is no race of men anywhere on earth so backward that it has no language, no set of speech sounds by which the people communicate with one mother．Furthermore, in historical times, there has never been a race of men without a language．

    Second, there is no such thing as a primitive language．There are many people whose cultures are undeveloped, who are, as we say, uncivilized. but the languages they speak are not primitive．In all known 1anguages we can see complexities that must have been ¹ tens of thousands of years in developing．

    This has not always been well understood；indeed, the direct contrary ²  has often been stated． Popular ideas of the language of the American Indians will illustrate．Many people have supposed that the Indians communicated in a very primitive system of noises．Study has proved this to be nonsense．There are, or were, hundreds of American Indian languages, and a11 of them rum out ³ to be very complicated and very old. They are certainly different from the languages that most of us are familiar with, but they are no more primitive than English and Greek ⁴．

    A third thing we know about language is that all languages are perfectly adequate．That is, each one is a perfect means of expressing the culture of the people who speak the language．

Finally, we know that language changes．It is natural and normal for language to change； the only languages which do not change are the dead ones．This is easy to understand if we look backward in time．Change goes on in all aspects of language．Grammatical features change as do speech sounds, and changes in vocabulary are sometimes very extensive and may occur very rapidly．Vocabulary is the least stable part of any language ⁵.

词汇：

race/[reɪs] n.种族

primitive [ˈprɪmətɪv] adj.原始的

uncivilized [ʌnˈsɪvəlaɪzd] adj.不开化的, 落后的

complexity [kəm"pleksətɪ] n.复杂性, 复杂现象

nonsense [ˈnɔnsəns] n.胡说, 没有根据的话

extensive/[ɪkˈstensɪv] adj.广泛的

vocabulary [və"kæbjələrɪ] n.词汇

注释：

1．must have( been) done:must+动词的完成式，表示对过去发生的事情的猜测。

2．the direct contrary:完全相反（的观点，看法）

3．turn out:结果（是），原来（是）

4．no more... than...：同……一样不……

In the second paragraph the author thinks that

A:some backward race doesn"t have a language of its own B:some race in history didn"t possess a language of its own C:any human race, whether backward or not, has a language D:some races on earth call communicate without language

已知正弦量u=220sin（314t+30°）V，则其电压最大值Um为（）V。

A:110 B:155 C:220 D:220

某一正弦交流电电压V=220sin314t伏，在t=0.005秒时，电压的瞬时值为（）伏。

B:220 C:220 D:110

已知正弦交流电压u＝220sin（314t－30°）则其角频率为（）。

A:30 B:220 C:50 D:100π

某正弦电压有效值为220V，频率为50Hz，在t=0时，u（0）=220V，则该正弦电压表达式为（）。

A:u=380sinl00πtV B:u=311sin(100πt+45°)V C:u=220sin(100πt+90°)V D:u=-311sin(100πt+45°)V

已知正弦交流电压u=220sin(314t-30°)则其角频率为( )。

A:30 B:220 C:50 D:100π

已知正弦交流电压u=220sin(314t-30°)则其角频率为( )。

A:30 B:220 C:50 D:100π

已知正弦交流电压u=220sin(314t-30°)则其角频率为( )。

A:30 B:220 C:50 D:100π