Alcohol itself has no significant carcinogenicity, but many epidemiological investigations have found that drinking is positively correlated with the risk of multiple cancers--that is, the incidence of multiple cancers has increased among people who drink alcohol. Which of the following, if true, would best support the above findings? ['Alcohol, the metabolite of alcohol in the body, can stably attach to DNA molecules, causing cancer or mutation.', 'Sweet and hard alcohol is widely consumed in Eastern Europe, where the incidence of esophageal cancer is high.', 'Tobacco contains a variety of carcinogenic components, and its metabolites in humans are similar to those of alcohol in humans.', 'Some scientists estimate that 80% of digestive tract cancers can be avoided if Americans quit smoking and drinking.']