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 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’s health and size.”

　　41. People who are cognitively healthy are those ______.

　　A. who can remember large amounts of information

　　B. who are highly intelligent

　　C. whose minds are alert and receptive

　　D. who are good at recognizing different sounds

　　42. According to Fozard’s argument, people can make their brains work more efficiently by ____.

　　A. constantly doing memory work

　　B. taking part in various mental activities

　　C. going through specific training

　　D. making frequent adjustments

　　43. 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. have been generally accepted

　　D. are practiced by the researchers themselves

　　44. Older people are generally advised to ______.

　　A. keep fit by going in for physical activities

　　B. keep mentally active by challenging their brains

　　C. maintain mental alertness through specific training

　　D. maintain a balance between individual and group activities

　　45. What is the passage mainly about?

　　A. How biochemical changes occur in the human brain?

　　B. Why people should keep active not only physically but also mentally?

　　C. How intellectual activities influence brain-cell health ?

　　D. Why people should receive special mental training as they age ?

　　Passage Two

　　The food we eat seems to have profound effects on our health. Although science has made enormous steps in making food more fit to eat, it has, at the same time, made many foods unfit to eat. Some research has shown that perhaps eighty percent of all human illnesses are related to diet and forty percent of cancer is related to the diet as well, especially cancer of the colon. Different cultures are prone to contract certain illnesses because of the food that is characteristic in these cultures. That food is related to illness is not a new discovery. In 1945, government researchers realized that nitrates (硝酸钾) and nitrites(亚硝酸盐), commonly used to preserve color in meats, and other food additives, caused cancer. Yet, these carcinogenic additives remain in our food, and it becomes more difficult all the time to know which things on the packaging labels of processed food are helpful or harmful. The additives which we eat are not all so direct. Farmers often give penicillin to beef and poultry and because of this, penicillin has been found in the milk of treated cows. Sometimes similar drugs are administered(given) to animals not for medicinal purposes, but for financial reasons. The farmers are simply trying to fatten the animals in order to obtain a higher price on the market. Although the Food and Drug Administration has tried repeatedly to control these procedures, the practices continue.