The correct answer is (b). Saliva helps in the digestion of starch by breaking it down into smaller molecules that can be easily absorbed by the body. Saliva contains an enzyme called amylase, which breaks down starch into maltose, a disaccharide. Maltose is then broken down into glucose, a monosaccharide, which can be absorbed by the body.
Option (a) is incorrect because saliva does not help in the digestion of protein. Protein is broken down by enzymes in the stomach and small intestine.
Option (c) is incorrect because saliva does not help in the digestion of fibers. Fibers are not broken down by enzymes in the digestive system. They are passed through the digestive system and excreted in the stool.
Option (d) is incorrect because saliva does not help in the digestion of fats. Fats are broken down by enzymes in the small intestine.