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问题 选择题

自然界中同种生物不同个体之间性状上的差异现象叫做（　　）

A．基因突变

B．性状分离

C．变异

D．遗传

答案

变异是指亲代间和子代个体间的差异．根据变异是否可以遗传，分为可遗传变异和不可遗传变异．由遗传物质改变引起的变异，能够遗传给后代的属于可遗传的变异；仅由环境因素引起的，遗传物质没有发生改变，也不能够遗传给后代的变异属于不可遗传的变异．因此，自然界中同种生物不同个体之间性状上的差异现象叫做变异．

故选：C

选择题

医学证明，大脑皮层受损，人就会变成为白痴。这说明

A．人脑是思维的源泉

B．只要有人脑就会有意识

C．人脑是思维的物质器官

D．意识的内容来自外部世界
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单项选择题

Watch a baby between six and nine months old, and you will observe the basic concepts of geometry being learned. Once the baby has mastered the idea that space is three-dimensional, it reached out and begins grasping various kinds of objects. It is then, from perhaps nine to fifteen months, that the concepts of sets and numbers are formed. So far, so good. But now an ominous development takes place. The nerve fibers in the brain insulate themselves in such a way that the baby begins to hear sounds very precisely. Soon it picks up language, and it is then brought into direct communication with adults. From this point on, it is usually downhill all the way for mathematics, because the child now becomes exposed to all the nonsense words and beliefs of the community into which it has been so unfortunate as to have been born. Nature having done very well by the child to this point, having permitted it the luxury of thinking for itself for eighteen months, now abandons it to the arbitrary conventions and beliefs of society. But at least the child knows something of geometry and numbers, and it will always retain some memory of the early happy days, no matter what vicissitudes it may suffer later on. The main reservoir of mathematical talent in any society is thus possessed by children who are about two years old, children who have just learned to speak fluently.

The word " vicissitude" (in boldface) in the context means().

A. change

B. transformation

C. variation

D. the rubs and worries of life
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