第三部分：阅读理解（共15小题；每小题2分，满分30分）
请认真阅读下列短文，从短文后各题所给的A、B、C、D四个选项中，选出最佳选项，并在答题卡上将该项涂黑。
A
Around the age of 40, honest people may already admit to noticing changes in their mental abilities. This is the beginning of a gradual decline that in all too many of us will end with full-blown dementia(痴呆).
However, a few drugs that might do the job, known as “cognitive enhancement(认知增强)”, are already on the market, and a few dozen others are on the way. Perhaps the best-known is modafinil. Licensed to treat narcolepsy, the condition that causes people to suddenly fall asleep, it has notable effects in healthy people too. Modafinil can keep a person awake and his or her attention fixed for 90 hours straight, with none of anxiety, nervousness and bad concentration. In fact, with the help of modafinil, people who can hardly go to sleep can perform even better than their well-rested, un-medicated(未服药的) selves.
It’s an open secret that many, perhaps most, prescriptions for modafinil are written not for people who suffer from narcolepsy, but for those who simply want to stay awake. Similarly, many people are using Ritalin not because they suffer from attention problem or any other disorder, but because they want superior concentration during exams or heavy-duty activities.
Some drugs have also been specially designed to improve memory. Many of these seem to work, and without any major side effects. So why aren’t we all on cognitive enhancers already?
“We need to be careful what we wish for,” says Daniele Piomelli at the University of California at Irvine. Repairing and improving memory may have unwanted effects, he warns. “Eventually we may end up remembering things we don’t want to.”
56. According to the message, we can learn that originally modafinil is a drug designed for _____.
A. for both healthy and unhealthy people
B. the treatment of dementia
C. people who can hardly go to sleep
D. those suffering from falling asleep suddenly
57. The passage mainly talks about _____.
A. dementia—a threat to the old people                     B. modafinil—a nice drug for dementia
C. relevant drugs to a better brain                      D. cognitive enhancement
58. The underlined sentences in paragraph two wants to tell us that _____.
A. without modafinil people suffering from sleep problems cannot rest well
B. people lacking sleep can work better than they are in a healthy state if taking modafinil
C. modafinil has greater effects on healthy people if they take it
D. with modafinil people suffering from narcolepsy can fall asleep easily
59. What’s the writer’s attitude to the drugs mentioned in the passage?
A. Positive.    B. Negative.    C. Objective(客观的).   D. Doubtful.