Which of the following most logically completes the argument?
Because tooth enamel can repair itself using fluoride, introducing fluoride into drinking water can improve the dental health of communities. However, the majority of all commercially available fluoride contains impurities that, when ingested, have negative health consequences for some of the population. Therefore, the introduction of a second chemical to fluoridated water, which neutralizes the impurities, would improve dental health in the affected communities, since _______.