A survey published in a leading medical journal in the earty 1970s found that the more frequently people engaged in aerobic exercise, the lower their risk of lung disease tended to be. Since other surveys have confirmed these results, it must be the case that aerobic exercise has a significant beneficial effect on people' s health. The reasoning above is questionable because the argument ["fails to consider that even infrequent aerobic exercise may have some beneficial effect on people's health", 'concludes merely from the fact that two things are correlated that one causes the other', 'ignores anecdotal evidenee and bases its conclusion entirely on scientific research', 'presumes, without providing justffication, that anyone who does not have lung disease is in good health']