在《红楼梦》中，薛宝钗的主要性格特点是什么？

吸烟与肺癌关系的许多研究都是前瞻性队列研究，最初调查过吸烟情况的研究对象中有一部分后来失访了，关于这些失访者下列说法正确的是

A．应从研究中剔除出去

B．只在随机化试验中才影响结果

C．其被随访到的那段时间应包括在暴露人年中

D．只有当这些失访者具有较高的肺癌危险度时，才会得出有偏差的相对危险度的估计值

E．因为进入研究时存在选择偏倚，可得出不正确的相对危险度估计值

患者女性，32岁。反复干咳，喘息，无诱因、季节性，伴乏力，纳差，少痰。当地医院诊断：支气管哮喘。给抗平喘、消炎，对症治疗，症状好转不明显，既往否认过敏史，无鼻炎史。病程中无发热，时有盗汗。查体：体温36.8℃，脉搏88次/分，双肺可闻及散在哮鸣音。实验室检查：WBC：8.9×10⁹/L，N：0.75，EOS正常。肺功能：FEV1：2.1L/S，占正常预计值73%，用药后增加210ml，缓解率11%。胸片：双肺可见散在斑点状阴影，双肺中野明显，右肺中野病灶似"树芽状"。

结核杆菌耐药性产生的机制是（）

A.自然突变株

B.适应学说

C.药物通透性降低

D.质粒介导

E.染色体突变

F.细胞膜蛋白位点改变

“如果给我一个支点，我能撬动整个地球！”这是哪位物理学家的话[ ]

A．阿基米德

B．爱迪生

C．牛顿

D．爱因斯坦

(46) History tells us that in ancient Babylon, the cradle of our civilization, the people tried to build a tower that would reach to heaven. But the tower became the tower of Babel, according to the Old Testament, when the people were suddenly caused to speak different languages. In modern New York City, a new tower, that of the United Nations Building, thrusts its shining mass skyward. (47) But the realization of the UN’s aspirations—and with it the hopes of the peoples of the world—is threatened by our contemporary Babel: about three thousand different languages are spoken throughout the world today, without counting the various dialects that confound communication between peoples of the same land.

In China, for example, hundreds of different dialects are spoken; people of some villages have trouble passing the time of day with the inhabitants of the next town. In the new African state of Ghana, five million people speak fifty different dialects. In India more than one hundred languages are spoken, of which only fourteen are recognized as official. To add to the confusion, as the old established empires are broken up and new states are formed, new official tongues spring up at an increasing rate.

In a world made smaller by jet travel, man is still isolated from many of his neighbors by the Babel barrier of multiplying languages. Communication is blocked daily in scores of ways. Travelers find it difficult to know the peoples of other nations. Scientists are often unable to read and benefit from the work being carried on by men of science in other countries. (48) The aims of international trade, of world accord, of meetings between nations, are blocked at every turn; the work of scholars, technologists, and humanists is handicapped. Even in the shining new tower of the United Nations in New York, speeches and discussions have to be translated and printed in the five official UN language—English, French, Spanish, Russian and Chinese. Confusion, delay, suspicion, and hard feelings are the products of the diplomatic Babel.

The chances for world unity are lessened if, in the literal sense of the phrase, we do not speak the same language. (49) We stand in dire need of a common tongue, a language that would cross national barriers, one simple enough to be universally learned by travelers, businessmen, government representatives, scholars, and even by children at school.

Of course, this isn’t a new idea. Just as everyone is against sin, so everyone is for a common language that would further communication between nations. (50) What with one thing and another—our natural state of drift as human beings, our rivalries, resentments, and jealousies as nations—we have up until now failed to take any action. I propose that we stop just talking about it, as Mark Twain said of the weather, and do something about it. We must make the concerted, massive effort it takes to reach agreement on the adoption of a single, common auxiliary tongue.

(48) The aims of international trade, of world accord, of meetings between nations, are blocked at every turn; the work of scholars, technologists, and humanists is handicapped

如何进行电除尘器电瓷部件的安装？