A recent study confirmed that salt intake tends to increase blood pressure and found that, as a result, people with high blood pressure who significantly cut their salt intake during the study had lower blood pressure by the end of the study. However, it was also found that some people who had very high salt intake both before and throughout the study maintained very low blood pressure. Which one of the following, if true, contributes the most to an explanation of the results of the study? ['At the beginning of the study, some people who had very low salt intake also had very high blood pressure.', 'For most people who have high blood pressure, reducing salt intake is not the most effective dietary change they can make to reduce their blood pressure.', 'Persons suffering from abnormally low blood pressure have heightened salt cravings, which ensure that their blood pressure does not drop too low.', 'Study participants with high blood pressure who cut their salt intake only slightly during the study did not have significantly lower blood pressure by the end of the study.']