Studies suggest that, for the vast majority of people who have normal blood pressure, any amount of sodium greater than that required by the body is simply excreted and does not significantly raise blood pressure. So only persons who have high blood pressure and whose bodies are incapable of safely processing excess sodium need to restrict their sodium intake. Which one of the following, if true, would most seriously weaken the argument? ['Every human being has a physiological need for at least some sodium.', 'Any sodium not used by the body will increase blood pressure unless it is excreted.', "Excess sodium intake over time often destroys the body's ability to process excess sodium.", 'High blood pressure is more harmful than was previously believed.']