[单项选择] Modern Drugs Doctors, sixty years ago, could do little to help victims of polio. Serious cases usually ended in death. In 1955, a vaccine was developed that prevented the disease. Today, polio is no longer a major health problem. Many of the most important drugs that doctors prescribe today have been developed in the last 30 years. Modern drugs are complex, specific and powerful. People need to know more about drugs in order to use them safely. Early people discovered by accident that some of the plants growing around them seemed useful to heal sores, relieve pain, or even cure diseases. These plants were the first drugs. Now plants are still the source of some drugs. Quinine, for example, is a bitter-tasting drug used to treat the chills and fever of malaria and to reduce attacks of the disease. It is made from the bark of the cinchona tree, which grows in the Andes Mountains. The Indians of that region were the first to use the bark as
A. Originally, quinine was made from some tree bark.
B. Quinine is used to cure malaria.
C. Now, the cinchona tree is no longer the only source of quinine.
D. It was the Spanish people who first used quinine as a medicine.