Producers of many mouthwash brands claim that using mouthwash prevents tooth decay. What is the best conclusion regarding these mouthwash brands and bacteria in the mouth?
a.Mouthwash contains ingredients that kill harmful bacteria.
b.Mouthwash contains helpful bacteria that produce oxygen.
c.Mouthwash does not really work because the growth of harmful bacteria cannot be prevented.
d.Mouthwash does not really work because bacteria is not known to directly cause tooth decay.