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A．To exercise and enjoy themselves.B．To race with professional athletes.C．To complete
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治疗慢性胃炎
A．simplerB．more complexC．ore meaninglessD．more troublesome
Children's Numerical Skills
People appear to be born to compute. The numerical skills of children develop so early and so inexorably that it is easy to imagine an internal clock of mathematical maturity guiding their growth. Not long after learning to walk and talk, they can set the table with impressive accuracy—one knife, one spoon, one fork, for each of the five chairs. Soon they are capable of noting that they have placed five knives, spoons and forks on the table and, a bit later, that this amounts to fifteen pieces of silverware. Having thus mastered addition, they move on to subtraction. It seems almost reasonable to expect that if a child were secluded on a desert island at birth and retrieved seven years later, he or she could enter a second-grade mathematics class without any serious problems of intellectual adjustment.
Of course, the truth is not so simple. This century, the work of cognitive psychologists has illuminated the subtle forms of daily learning on which intellectual progress depends. Children were observed as they slowly grasped—or, as the case might be, bumped into—concepts that adults take for granted, as they refused, for instance, to concede that quantity is unchanged as water pours from a short stout glass into a tall thin one. Psychologists have since demonstrated that young children, asked to count the pencils in a pile, readily report the number of blue or red pencils, but must be coaxed into finding the total. Such studies have suggested that the rudiments of mathematics are mastered gradually, and with effort. They have also suggested that the very concept of abstract numbers—the idea of a oneness, a two ness, a three ness that applies to any class of objects and is a prerequisite for doing anything more mathematically demanding than setting a table—is itself far from innate.
Children can set table even before they can walk and talk.
Many people imagine that Alzheimer's disease (早老性痴呆病), the degenerative disorder that ultimately leaves sufferers with total memory loss, is an inevitable result of aging. This is not so. 【C1】______ the risks of contracting the disease increase with age, there are many elderly people【C2】______ memories are perfect. Most of us are so ill-【C3】______ about all forms of memory loss that we label everything as "Alzheimer's'. Alzheimer's disease itself can【C4】______ people as young as 30 and can progress either quickly or slowly. It can also【C5】______ the blame for other non-degenerative conditions such as deep depression.【C6】______ , only an examination of the brain tissue during an autopsy (解剖) can produce an accurate【C7】______ of the disease.
The causes of Alzheimer's are unknown. They may be either【C8】______ or environmental. A study in 1996 of 13,000 people whose parents or siblings had the disease showed they had five times【C9】______ chance of succumbing 【C10】______ the age of 80 than those with no family【C11】______ of the problem.
There are other factors, however. In a study of identical twins, it was found that only about half of the twin pairs developed Alzheimer's and, when both twins【C12】______ . it, they did so as【C13】______ as 15 years apart. The possibility【C14】______ environment plays a part was【C15】______ by another 1996 study, this time of two groups of elderly Japanese men. One group lived in Hawaii, the other in Japan. The Hawaiian group had a much higher【C16】______ of the disease.
Aluminum has been blamed for the development of Alzheimer's. This is because a high level of aluminum has been found in the brains of sufferers. The disease was first diagnosed at the beginning of the 20th century. It was at this time【C17】______ aluminum was becoming widely available for use in cooking pots.
Memory loss, difficulty in【C18】______ familiar tasks, and problems with abstract thinking are all【C19】______ of the onset of the disease. One unusual feature is its impact on language. It attacks nouns first,【C20】______ verbs. Grammar is one of the last things to go.
【C1】
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