Concept:Tooth decay occurs when acids produced from sugar by mouth bacteria damage the tooth enamel.Explanation:Bacteria naturally present in the mouth feed on sugars left on the teeth.These bacteria metabolize sugar and release acids as a waste product.The acids slowly dissolve the hard enamel layer of the teeth.This destruction of enamel creates cavities and leads to tooth decay.So, the main cause is bacterial acid production from sugar, not the amount of food eaten.Answer:C. the bacteria in the mouth that metabolize sugar to acids