Passage 3
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 (接受能力强的) 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 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 skill, both because they 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 influences brain-cell health and size.”
People who are cognitively healthy are those ________.
文章第二段提到“People will be alert (警觉的) and receptive (接受能力强的) if they are faced with…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.”，可知那些思维警觉，接受能力强的人在认知思维上更加健康。因此本题答案选C。
According to Fozard's argument people can make their brains work more efficiently by ________.
文章第三段最后一句提到“they are sure that their range of activities will help the way their brains work.”，他们确信自己的活动领域有助于大脑工作的方式。他们认为参加各种脑力活动可以让大脑更有效地工作，选项B正确。
The findings of James and other scientists in their work ________.
文章第三段第一句提到“Many experts are so convinced of the benefits of challenging the brain that they are putting, the theory to work in their own lives”，许多专家确信，向大脑提出挑战是极有好处的，因此他们将这一理论应于自己身上。选项D表述与原文意思相符，因此答案选D。
Older people are generally advised to ________.
文章最后一段提到“Cohen says that we are frequently advised to keep physically active as we age, but older people need to keep mentally active as well”，Cohen说我们通常得到的建议时在年纪增长时要保持身体健康，但老人也需要保持精神上的活力。因此老年人通常是被建议要进行身体锻炼保证身体健康，本题答案选A。
What is the passage mainly about?
文章主要探讨了为什么人要保持身体与思维两方面的活跃以及保持思维活跃的做法和好处，选项B的表述最能体现文章主旨，因此答案选B。