A、Vitamin B B、Vitamin C C、Vitamin D D、Vitamin A A文章最后说“too much vitamin B can damage the nerves”，故选A。

Most people probably do not need to take vitamin pills to improve their health. Yet millions of people do. In the United States 40 percent of the people reportedly take vitamin pills.
    The American Medical Association noted that vitamins can help keep people healthy when used correctly. For example, children may need to take vitamins for a while; pregnant women and women breast-feeding their children may need vitamins; people who do not eat meat or are eating less food to lose weight may need them. In general, other people do not. But they should try to eat moderate amounts of all kinds of foods — fruits and vegetables, grains, milk products, and meat and fish.
    About half of all Americans who take vitamins use small amounts just to increase their vitamin levels a little. Dr. Callaway notes those daily levels are already a little higher than we need for good health. The health care groups say these people probably are not harming themselves. The other half uses large amounts in an effort to prevent some things as cancer and heart disease. Callaway says that there’s no proof that this works. And huge amounts of vitamins, he says, can be harmful. For example, too much vitamin A can damage the liver and bones; too much vitamin B can damage the nerves; too much vitamin C or vitamin D may produce kidney stones.
Questions 21-25 are based on the passage you have just heard.
21. What may damage one’s nerves if being taken too much?
22. What should those who don’t have to take vitamin eat?
23. In the U.S.A. how many people are reported to take vitamin?
24. Which group of people need to take vitamin?
25. Which of the following statements is NOT true according to the passage?