A) constantly doing memory work
B) making frequent adjustments
C) going through specific training
D) taking part in various mental activities
注：考第三段末句。
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 dont need that kind of skill. 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 they enjoy them and because they are sure that their range of activities will help the way their brains work.
23. The findings of James and other scientists in their work _________.
A) remain a theory to be further proved
B) have been challenged by many other experts
C) are practised by the researchers themselves
D) have been generally accepted
注：第三段首句中的theory等同于findings。
