The reasons for a person’s becoming an alcoholic have often been debated by psychologists and other scientists. But recent studies suggest that the problem of alcoholism(酒精中毒) should also be the focus of investigation by biologists. While such things as hard jobs, boredom, and unhappiness can lead to alcoholism, researchers at a prominent university have found that there may also be a genetic factor involved in alcoholism. In the study, children of alcoholic parents were surveyed. The result showed that the children of alcoholic parents were more likely to become alcoholics themselves than were children of non-drinking parents. This evidence in itself is not conclusive（确信的）about anything. After all, it may be the constant exposure（接触）and easy access to alcohol that cause the children of alcoholics to become alcoholics themselves. But there is more evidence. The study found that children born of alcoholic parents but raised by non-drinking foster（抚养的）parents also were susceptible to alcoholism. This group of offspring（后代）was more likely to take up drinking than youngsters who were born of and raised by non-drinking parents. Other evidence found in the study suggests that environment does not play as important a role in the development of alcoholism as had been previously thought. The study found that the likelihood of alcoholism was better predicted from the characteristics of the parents than from such environmental characteristics as type of job or level of income. 63. What is the main point of the passage? A. To describe the environment in the development of alcoholism. B. To study the psychological factor in the development of alcoholism. C. To describe how the children of alcoholic parents become alcoholics themselves. D. To describe the close link between genetic make-up and alcoholism. 64. According to the passage, what can bring about alcoholism? A. Biologists’ investigation.                       B. Non-drinking parents. C. Hard jobs, boredom and unhappiness.             D. Foster parents’ raising. 65. According to the findings of the study, who would be the most likely to become an alcoholic? A. A person who had a hard job. B. A person who was born of alcoholic parents. C. A person who was raised by drinking foster parents. D. A person who was born of and raised by non-drinking parents. 66. According to the passage, what should the problem of alcoholism be treated as? A. A psychological problem. B. An environmental problem. C. A biological problem. D. An educational problem.