请教大家一个英语问题——有兴趣的进来看看

gubinlaile

Researchers have established that when people are mentally engaged , biochemical changes occur in the brain that allow it to act more effectively in cognitive (认知的)areas such as attention and memory. This is true regardless of age.
　　People will be alert (警觉的)and receptive (愿意接受的)if they are faced with information that gets them to think about things they are interested in. And someone with a history of doing more rather than less will go into old age more cognitively sound than someone who has not had an active mind.
　　Many experts are so convinced of the benefits of challenging the brain that they are putting the theory to work in their own lives. "The idea is not necessarily to learn to memorize enormous amounts of information," says James Fozard, associate director of the National Institute on Aging. "Most of us don't need that kind of skii1.Such specific training is of less interest than being able to maintain mental alertness. "Fozard and others say they challenge their brains with different mental skills, both because t hey enjoy them and because they are sure that their range of activities will help the way their brains work.
　　Gene Cohen ,acting director of the same institute ,suggests that people in their old age should engage in mental and physical activities individually as well as in groups. Cohen says that we are frequently advised to keep physically active as we age, but older people need to keep mentally active as well. Those who do are more likely to maintain their intellectual abilities and to be generally happier and better adjusted. "The point is, you need to do both," Cohen says. "Intellectual activity actually influences brain-cell health and size."
问题："The idea is not necessarily to learn to memorize enormous amounts of information,"
此句中为何用necessarily而不是用necessary?

[ 本帖最后由 gubinlaile 于 2007-7-16 00:07 编辑 ]