The word "it" in the saying "use it or lose it" (p

单项选择题

Researchers disagree whether the "use it or lose it" philosophy holds for cognitive aging, but there is one evidence that keeping mentally active can slow age-related declines.
At Pennsylvania State University, Sherry Willis and her husband, K. Warner Schaie, have studied 5000 people, some since 1956. People lucky enough to avoid chronic diseases may also fare better in intellectual function, they find, perhaps because chronic diseases can restrict lifestyle and reduce mental stimulation. Similarly, those lucky enough to be relatively affluent also fare better, perhaps because money can buy intellectually stimulating things like travel.
Education helps, too, researchers say because of instills the conviction that you can always learn something new. The Schaie-Willis team also has some other observations. Being in a stable marriage with a stimulating spouse, they say, helps maintain intellectual vigor.
Flexibility counts too. People who stay mentally vibrant are often those who do not insist that "they must do things today as they did before" Schaie says. In neuropsychological terms, the ability to see problems in new ways often yields higher scores on tests of-mental function. And people satisfied with life also stay more mentally fit, he says.
If you find your mental skills sagging, consider working on specific deficits. When Willis gave 5-hour tutorials on inductive reasoning or spatial skills to about 200 people whose skills had declined in the previous 14 years, 40 percent regained lost abilities. That advantage held up seven years late when they were retested.
Other ways to stay sharp, Schaie says, are doing jigsaw puzzles to hone visuo-spatial skills, working crossword puzzles for verbal skills, playing bridge for memory and simply matching wits at home with players on TV game shows.
Finally, remember this. Even though you may lose some mental skills with normal aging, you also gain in one key area: wisdom. The growth of wisdom continues throughout the 40s, 50s and even 60s.

The word "it" in the saying "use it or lose it" (paragraph 1) refer to ______.

A．brain power
B．cognitive development
C．mental stimulating
D．intellectual function