单选题
Watch a baby between six and nine months old, and you will observe the basic idea of geometry being learned. Once the baby has mastered the idea that space is three dimensional, it reaches out and begins grasping various things, that the ideas of sets and numbers are formed. So far, so good. But now an ominous development takes place. The nerve fibers in the brain separate themselves in such a way that the baby begins to hear sounds very exactly. Soon it picks up language. And it is then brought into direct communication with grown-ups. From this point on, it is usually downhill all the way for mathematics, because the child now becomes exposed to all the rubbish words and beliefs of the 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 gives it up to the unreasonable conventions and beliefs of society. But at least the child knows something of geometry and peaceful days, no matter what vicissitudes(兴衰变迁)it may suffer later on. The main reservoir of mathematical ability in any society is thus possessed by children who are about two years old, children who have just learned to speak freely.