Studies have found that human tears contain many of the same hormones that the human body produces in times of emotional stress. Hence, shedding tears removes significant quantities of these hormones from the body. Ttherefore, crying must have the effect of reducing emotional stress. The reasoning in the argument is most vulnerable to criticism on the grounds that the argument ['overlooks the possibility that if crying has a tendency to reduce emotional stress, this tendency might arise because of something other than the shedding of tears', 'takes for granted that because certain substances are present whenever a condition occurs, those substances are a cause of that condition', 'fails to adequately distinguish between two distinct factors that are jointly responsible for causing a given phenomenon', 'confuses a condition that is required for the production of a given phenomenon with a condition that in itself would be sufficient to cause the production of that phenomenon']