单项选择题

During the 9th century scientists found that when certain parts of the brain of a man were (36) , he would lose the (37) to do certain things. And so, people thought that each part of the brain does a different (38) . But modern research has (39) out that this is not so, for it is not (40) to say (41) what each part of the brain does.
In the past fifty years there (42) a great increase in the amount of research (43) on the brain. Chemists and biologists have (44) that the (45) the brain works it is not so (46) as people in general may think. Chemists tell us that 100,000 chemical changes (47) in the brain every second. Some recent researches also (48) that we can remember everything (49) happens (50) us. We (51) not be able to recall (回忆) the things we’ve heard and seen, but it is all kept there in the storehouse of the human mind.
Earlier scientists thought the power of one’s brain got weaker as one grow (52) . But it is now thought that is not (53) . As long as the brain is (54) (55) exercise it keeps its ability. It has been proved that an old person who has (56) been active in the mind has a (57) mind than a young person who has only done (58) work (59) using much of his brain. It is now thought that the (60) work we give our brains, the more work they are able to do.

59().

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