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问题 选择题

根据化学方程式：2H2S+3O2

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2H2O+2X推知X的化学式是（　　）

A．S

B．SO2

C．SO3

D．H2SO4

答案

由化学方程式为2H2S+3O2

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2H2O+2X，

根据质量守恒定律可知，反应前后的元素种类和原子个数不变，

H原子的个数在反应前后相等，而S、O原子的个数不等，

由元素守恒和原子守恒，则X中有S、O元素，且有2个S原子、4个O原子，

又X的化学计量数为2，则X的化学式为SO2，

故选B．

单项选择题

引起较为明显的脑水肿的放射治疗方式为（）。

A.超分割放射治疗

B.γ–刀或Χ–刀

C.常规普通放射治疗

D.3D－γCRT

E.IMRT
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单项选择题

Aristotle was one of those who could found a civilization, and while he thought of education as both a social value and an end in itself, he ascribed its chief importance (21) what might be considered a third basic concept of education: to train the mind to think, (22) what it is thinking about. The key is not (23) it knows but how it (24) any new fact or argument. "An educated man," Aristotle wrote in On the Parts of Animals, "should be able to (25) a fair offhand judgment as to the goodness or badness of the method used by a professor in his exposition. To be (26) is in fact to be able to do this."
The Aristotle view of education as a (27) has become the conventionally worthy answer today (28) college presidents and other academic leaders are asked what an education should be. An educated man, says Harvard President Bok, (29) a deep breath, must have a "curiosity in (30) the unfamiliar and unexpected, an open-mindedness in entertaining opposing points of view, (31) for the ambiguity that surrounds so many important issues, and a willingness to make the best decision he can in the fact of uncertainty and doubt."
This is an approach that appears to (32) more importance to the process of learning (33) to the substance of what is learned. The very old notion of the generalist who could comprehend all subjects has (34) been an impossibility. To make matters (35) more difficult, the fields of knowledge keep changing.

A. known B. educatedC. literate D. wise
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