Concept:Rice is mainly a carbohydrate, so its digestion starts where carbohydrate-digesting enzymes are present.Explanation:Digestion of rice (starch) begins in the mouth.Saliva contains the enzyme amylase.Amylase breaks down starch into maltose, a simpler sugar.Therefore, the first site of digestion is the mouth, not the stomach, gullet, or colon.Answer:C. mouth.