Directions: There are four passages in this part. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A., B., C. and D. You should decide on the best choice and mark the corresponding letter on the Answer Sheet.

Passage Four

The field of medicine has always attracted its share of quacks（庸医） . The reasons why quackery thrives even in modern times are not hard to find. To begin with, pain seems to be a chronic human condition. A person who suffers from some illness for a long time will pay any amount of money for the promise of relief. Second, even the best medical treatment cannot cure all the ills. Third, many people lack the training necessary to evaluate medical claims. However, most remedies sold by quacks are not only useless, but often can be harmful to the user as well. By far the most potent reason that quack medicines still are sold around the world has to do with the power of “mind over matter”. Your brain is the master organ of your body: It regulates all the chemical processes that keep you alive and well. When you become depressed and lose hope, your autonomic nervous system（植物神经系统） slows down these bodily processes and retards your chances of getting well. When you have hope and faith, these processes are sped up. You are thus likely to recover even from the most dreadful diseases.

The doctor who can convince the patients of their recovery cures more patients than the one whose behavior causes patients to lose faith in themselves. If a patient mistakenly believes that his condition can be cured by taking a drug of some kind, most physicians are happy to give him a placebo. The placebo does no harm at all, but it may so help the patient psychologically that the person’s pain diminishes and the patient may actually recover much faster than without taking the pill. Indeed, placebos may even have a physiological effect.