What is the function of the enzyme amylase?

Hint: Almost all enzymes are proteins that catalyse the biochemical reactions in living cells, hence called biocatalysts. Enzymes are proteinaceous in nature with the exception of recently discovered two RNA enzymes- Ribozyme, isolated from Tetrahymena and Ribonuclease isolated from bacteria.

Complete answer:
The correct option (D) increases the rate of starch breaking down into maltose. The process of digestion is accomplished by mechanical and chemical processes.
The chemical process of digestion is initiated in the buccal cavity.
Breaks down the substrate into amino acids- Amylase is basically a carbohydrate splitting enzyme,so it cannot split the substrate that is a carbohydrate into an amino acid. A carbohydrate is always split into its constituent sugars; a protein is split into amino acids. Pepsin is a proteolytic enzyme present in the gastrointestinal tract that hydrolyses proteins in the stomach.
Changes the product into the substrate- and enzyme does not start a chemical reaction but only increases the rate of chemical reaction. They do not change the equilibrium but bring about the equilibrium. Amylase is an enzyme which acts upon the substrate to give out the product.
Increases the rate of starch breaking down into glucose- Salivary amylase hydrolyses about 30 percent of starch into a disaccharide molecule i.e., maltose.
Increases the rate of starch breaking down into maltose- amylase has a hydrolytic action on starch which breaks it down into maltose. This enzyme works efficiently at a pH of 6.8.

The lysozyme present in the saliva acts as an antibacterial agent that prevents infections. The mass of food, now called ‘bolus’ is then pushed down through the pharynx into the esophagus. This process is called swallowing or deglutition. This occurs with the help of muscular contractions known as peristalsis. There is a sphincter between the esophagus and stomach called gastro-esophageal sphincter. It controls the passage of food into the stomach.

Note:
The saliva secreted into the oral cavity contains electrolytes like $Na^+$, $K^+$, $Cl^-$, $HCO^{3-}$ and enzymes like amylase and lysozyme. Salivary amylase is absent from the saliva of many mammals like cows, buffaloes and predatory carnivores like lions and tigers. However, pigs have got amylase in their saliva.