Correct Answer: A
Explanation:
Ptyalin is a protein found in saliva that breaks down the insoluble starch found in foods into smaller, soluble sugar fragments. This is another name for the amylase found in saliva, known as salivary amylase. This particular type of amylase is found only in humans.
Foods such as potatoes and rice contain a lot of starch, a carbohydrate. Starch is an insoluble polysaccharide — a long chain of sugars. The sugar in this case is glucose, and there are branches coming off of the chain.