Part ADirections: Read the following three texts. Answer the questions on each text by choosing A, B, C or D. Mark your answers on ANSWER SHEET 1.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 and receptive 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 mounts 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 skills, 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 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."People who are cognitively healthy are thoseA．who are highly intelligentB．whose minds ate alert and receptiveC．who can remember large amounts of informationD．who are good at recognizing different sounds