风管垂直安装，间距不应大于（），且单根直管至少应有2个固定点。 A.4m B.4

镁铝碱式盐对工业污水中的铬有良好吸附性。取该碱式盐0.7525g，滴加1.0mol/L盐酸，当加盐酸21.25mL时开始产生CO₂气体，加入盐酸至22.50mL时恰好反应完全，向该溶液中加入过量氢氧化钠溶液，过滤，沉淀物进行干燥后重0.4350g。则该碱式盐的化学式是

A．Al₂Mg₆(OH)₁₆CO₃∙4H₂O

B．Al₄Mg₁₂(OH)₃₄CO₃∙8H₂O

C．Al₂Mg₄(OH)₁₆CO₃∙4H₂O

D．Al₃Mg₆(OH)₃₄CO₃∙8H₂O

大致了解患儿视力情况的检查是()

A．注视反射

B．跟随反射

C．优先观看法

D．视觉诱发电位

E．光感测定

转向系可分为（）。

A、液压转向

B、机械转向

C、动力转向

D、轴转向

E、轮转向

反映肝细胞损伤最灵敏的血清学指标是

A．ALT
B．总蛋白
C．血糖降低
D．甘油三酯
E．胆汁酸

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.

The title which best expresses the idea of this text is（）

A. Progress in Pure Science

B. Learning for Its Own Sake

C. Man’s Science and Inventions

D. Difference between Science and Technology