问题 选择题

人体正常的血红蛋白中应含Fe2+.若误食亚硝酸钠,则导致血红蛋白中的Fe2+转化为高铁血红蛋白而中毒.服用维生素C可解除亚硝酸钠中毒.下列叙述中正确的是(  )

A.亚硝酸钠表现了还原性

B.维生素C表现了还原性

C.维生素C将Fe3+氧化成Fe2+

D.亚硝酸钠被氧化

答案

A.亚硝酸钠导致血红蛋白中的Fe2+转化为高铁血红蛋白而中毒,Fe元素的化合价升高,则亚硝酸钠表现了氧化性,故A错误;

B.服用维生素C可解除亚硝酸钠中毒,则服用维生素C中某元素的化合价升高,所以维生素C表现了还原性,故B正确;

C.维生素C将Fe3+还原成Fe2+,故C错误;

D.亚硝酸钠被还原,故D错误;

故选B.

名词解释
单项选择题

For me, scientific knowledge is divided into mathematical sciences, natural sciences or sciences dealing with the natural world (physical and biological sciences), and sciences dealing with mankind (psychology, sociology, all the sciences of cultural achievements, every kind of historical knowledge).

Apart from these sciences is philosophy, about which we will talk later. In the first place, all this is pure or theoretical knowledge, sought only for the purpose of understanding, in order to fulfill the need to understand that is intrinsic and con-substantial to man. What distinguishes man from animals is that he knows and needs to know. If man did not know that the world existed, and that the world was of a certain kind, that he was in the world and that he himself was of a certain kind, he wouldn’t be man. The technical aspects or applications of knowledge are equally necessary for man and are of the greatest importance, because they also contribute to defining him as man and permit him to pursue a life increasingly more truly human.

But even while enjoying the results of technical progress, man must defend the primacy and autonomy of pure knowledge. Knowledge sought directly for its practical applications will have immediate and foreseeable success, but not the kind of important result whose revolutionary scope is for the most part unforeseen, except by the imagination of the Utopians. Let me recall a well-known example. If the Greek mathematicians had not applied themselves to the investigation of conic section zealously and without the least suspicion that it might someday be useful, it would not have been possible centuries later to navigate far from shore. The first men to study the nature of electricity could not imagine that their experiments, carried on because o mere intellectual curiosity, would eventually lead to modern electrical technology, without which we can scarcely conceive o contemporary life.

Pure knowledge is valuable for its own sake, because the human spirit cannot resign itself to ignorance. But, in addition, it is the foundation for practical results that would not have been reached if this knowledge had not been sought disinterestedly.

In the author’s view, the Greeks who studied conic sections()

A. were mathematicians

B. worked with electricity

C. were interested in navigation

D. were unaware of the value of their studies