Passage One
　　For years, doctors advised their patients that the only thing taking multivitamins does is give them expensive urine (尿). After all, true vitamin deficiencies are practically unheard of in industrialized countries. Now it seems those doctors may have been wrong. The results of a growing number of studies suggest that even a modest vitamin shortfall can be harmful to your health. Although proof of the benefits of multivitamins is still far from certain, the few dollars you spend on them is probably a good investment.
　　Or at least that's the argument put forward in the New England Journal of Medicine. Ideally, say Dr. Walter Willett and Dr. Meir Stampfer of Harvard, all vitamin supplements would be evaluated in scientifically rigorous clinical trials. But those studies can take a long time and often raise more questions than they answer. At some point, while researchers work on figuring out where the truth lies, it just makes sense to say the potential benefit outweighs the cost.
　　The best evidence to date concerns folate, one of the B vitamins. It's been proved to limit the number of defects in embryos ( 胚胎 ), and a recent trial found that folate in combination with vitamin B 12 and a form of B6 also decreases the re-blockage of arteries after surgical repair.
　　The news on vitamin E has been more mixed. Healthy folks who take 400 international units daily for at least two years appear somewhat less likely to develop heart disease. But when doctors give vitamin E to patients who already have heart disease, the vitamin doesn't seem to help. It may turn out that vitamin E plays a role in prevention but cannot undo serious damage.
　　Despite vitamin C's great popularity, consuming large amounts of it still has not been positively linked to any great benefit. The body quickly becomes saturated with C and simply excretes ( 排泄 ) any excess.
　　The multivitamins question boils down to this: Do you need to wait until all the evidence is in before you take them, or are you willing to accept that there's enough evidence that they don't hurt and could help?
　　If the latter, there's no need to go to extremes and buy the biggest 'horse pills or the most expensive bottles. Large doses can cause trouble, including excessive bleeding and nervous system problems.
　　Multivitamins are no substitute for exercise and a balanced diet, of course. As long as you understand that any potential benefit is modest and subject to further refinement, taking a daily multivitamin makes a lot of sense.

　　21. At one time doctors discouraged taking multivitamins because they believed that multivitamins____.
　　A) could not easily be absorbed by the human body
　　B) were potentially harmful to people's health
　　C) were too expensive for daily consumption
　　D) could not provide any cure for vitamin deficiencies

　　22. According to the author, clinical trials of vitamin supplements____.
　　A) often result in misleading conclusions
　　B) take time and will not produce conclusive results
　　C) should be conducted by scientists on a larger scale
　　D) appear to be a sheer waste of time and resources

　　23. It has been found that vitamin E_____.
　　A) should be taken by patients regularly and persistently
　　B) can effectively reduce the recurrence of heart disease
　　C) has a preventive but not curative effect on heart disease
　　D) should be given to patients with heart disease as early as possible

　　24. It can be seen that large doses of multivitamins_____.
　　A) may bring about serious side effects
　　B) may help prevent excessive bleeding
　　C) are likely to induce the blockage of arteries
　　D) are advisable for those with vitamin deficiencies

　　25. The author concludes the passage with the advice that_____.
　　A) the benefit of daily multivitamin intake outweighs that of exercise and a balanced diet
　　B) it's risky to take multivitamins without knowing their specific function
　　C) the potential benefit of multivitamins can never be overestimated
　　D) it's reasonable to take a rational dose of multivitamins daily