Concept:Ptyalin is a starch-digesting enzyme present in the mouth.Explanation:Ptyalin is another name for salivary amylase.This enzyme is secreted by the salivary glands into the mouth, where it begins the digestion of cooked starch.It breaks down starch into maltose.Gastric juice, pancreatic juice, and succus entericus do not contain ptyalin.Therefore, the juice that contains ptyalin is saliva.Answer:D. Saliva