A Study of 6,600 Men Found That Those Who Consumed

A study of 6,600 men found that those who consumed a moderate amount of alcohol (one drink or less per night) have lower mortality (on the average) than those who drink none. Is this good evidence that drinking a moderate amount causes lower mortality?

A) Yes, because the study is an experiment.
B) No, because people who drink a moderate amount may differ from nondrinkers in other ways, such as income and exercise, that affect mortality.
C) Yes, because the sample is so large that the margin of error will be quite small.
D) No, because we can't generalize from 6,600 people to the millions of adults in the country.