采用刀具左补偿加工时，铣削加工为顺铣。

下列说法错误的是 [ ]

A．犯罪历来是国家法律打击的重点

B．在生活中，调节我们行为的规则有很多种

C．法律是公安行为规范

D．法律是社会行为规范

向一定质量的稀硫酸中加入锌粉至过量，下列图象合理的是（　　）

A．

B．

C．

D．

Although man has known asbestos for many hundreds of years, it was not until 160 years ago that it was mined for the first time on the North American continent. H. W. Johns, owner of a New York City Supply Shop for roofers, was responsible for the opening of that first mine.

Mr. Johns was given a piece of asbestos which had been found in Italy. He experimented with the material and then showed its surprising powers to his customers. After putting on a pair of asbestos gloves, which looked much like ordinary work gloves, he took red-hot coals from the fireplace and played with them in his hands. How astonished the customers were to discover that he was not burned at all. You can well imagine that he had increasing business in asbestos roofing materials. However, because it was very expensive to transport (carry) them from Italy to the United States, Mr. Johns sent out a young scientist to seek a source nearer home. This young man found great vein, in the province of Quebec in Canada.

Ever since 1881 Quebec has led the world in the production of this unusual mineral, which is made up of magnesium, silicon, iron, and oxygen. When it is mined, the asbestos is heavy, just as you would expect a mineral to be. When it is separated, a strange thing happens: the rock breaks down into fine, soft, soapy fibres.

Scientists do not know why the rock can be separated easily into threads, but they have found thousands of uses of this fireproof material, of the so-called "cloth of stone".

Which is the most important character of asbestos that the author wants to show us（）

A. It is like thread.

B. It feels soapy.

C. It burns easily.

D. It is unusually heavy.

在高疟区，主要用于病因性预防的药物是

A．乙胺嘧啶

B．奎宁

C．氯喹

D．伯氨喹

E．青蒿素

若有语句　　int i=-19,j=i%4;　　printf("%d\n",j);　　则输出的结果是【 】。