单选题：Exercising Your Memory　　1 Aging does not mean a dramatic dec

Exercising Your Memory
　　1 Aging does not mean a dramatic decline in memory power, unless you help it
happen by letting your mind go.

　　2 That's not to say that memory doesn't change throughout life. Researchers divide
memory into categories based on the length of time when memories are stored. One
system divides it up as short-term (less than one minute; remembering a telephone
number while you dial, for instance), long-term (over a period of years) and very
long-term memory (over a lifetime).

　　3 Short-term memory isn't mastered until about age 7, but after that you never lose it.　Long-term memory, however, involves more effort and skill and changes more through　life. It's not until the early teens (十几岁) that most people develop a mature long-term　memory.

　　4 First, we must get information into our heads through learning. Learning strategies　can get rusty (生锈的) without constant use. High school and college students, who are　forced to repeatedly exercise their long-term memory abilities (at least long-term enough　to get them through a final exam), usually do well on memory tests. The longer you stay　in school, the more chance you get to polish your learning, skills. It's no wonder that more　highly educated people have more effective memory skills throughout life.

　　5 Although older people in general learn somewhat more slowly than they did-when
younger, a dramatic difference exists between those who stay intellectually active --reading, discussing, taking classes, thinking -- and those who do not. Giving the brain a　daily workout (锻炼) is just as important as exercising your muscles. Brainwork keeps　your learning strategies in shape, and this helps your memory to function at full capacity.

　　6 The next part of a healthy long-term memory is retention (记忆力), the ability to store　what you have learned. Memory researchers still do not know whether memories are lost--whether they still exist in the brain but our mental searching cannot turn them up, or have disappeared entirely as our brain ages.

　　7 The third necessity for memory is recall, the ability to bring to mind the memories we have stored. Again, while aging has widely different effects on the recall abilities of different people, research indicates that the older we get, the longer it takes to recall facts. But slower recall is still recall. In fact, aging does not seem to have any effect on forgetting at all, which takes place at the same rate in younger and older people.
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