A、Genetics. B、Environment. C、Pressure form life. D、All of the above. D文中最后提到饮酒与基因、环境和生活的压力都有关。故答案为D。

For most people who drink, alcohol is a pleasant accompaniment to social activities. Moderate alcohol use — up to two drinks per day for men and one drink per day for women and older people — is not harmful for most adults. Nonetheless, a large number of people get into serious trouble because of their drinking. Currently, nearly 17.6 million adult Americans abuse alcohol or are alcoholic. Several million more adults engage in risky drinking that could lead to alcohol problems. These patterns include binge drinking and heavy drinking on a regular basis. In addition, 53 percent of men and women in the United States report that one or more of their close relatives have a drinking problem.
    The consequences of alcohol misuse are serious — in many cases, life threatening. Heavy drinking can increase the risk for certain cancers, especially those of the liver, esophagus, throat, and larynx. Heavy drinking can also cause liver cirrhosis, immune system problems, brain damage, and harm to the fetus during pregnancy. In addition, drinking increases the risk of death from automobile crashes as well as recreational and on-the-job injuries. Furthermore, both homicides and suicides are more likely to be committed by persons who have been drinking.
    Alcoholism, also known as "alcohol dependence", is a disease that includes four symptoms: craving, loss of control, physical dependence and tolerance. Withdrawal symptoms, such as nausea, sweating, shakiness, and anxiety, occur when alcohol use is stopped after a period of heavy drinking.
    Many people wonder why some individuals can use alcohol without problems but others cannot.
    One important reason has to do with genetics. Scientists have found that having an alcoholic family member makes it more likely that if you choose to drink you too may develop alcoholism. Genes, however, are not the whole story. In fact, scientists now believe that certain factors in a person’s environment influence whether a person with a genetic risk for alcoholism ever develops the disease. A person’s risk for developing alcoholism can increase based on the person’s environment, including where and how he or she lives; family, friends, and culture; peer pressure; and even how easy it is to get alcohol.
    Questions 21-25 are based on the passage you have just heard:
    21. How many adult Americans are alcoholic?
    22. What patterns can be included as signs of alcohol problems?
    23. What cancers can be resulted from alcohol misuse?
    24. What symptom will occur after alcohol use is stopped?
    25. What can be the reasons for alcoholism?