The human stomach is lined with glands that produce several chemicals that help in the process of digestion. One of these chemicals is hydrochloric acid, a powerful acid that makes the stomach very low in pH. Another substance is mucus--this substance lubricates and protects the stomach wall. A third substance is the enzyme pepsin which helps to break down protein molecules into smaller molecules called peptides. If the chemical enzyme pepsin was mixed with some proteins in a test tube in a laboratory, which of these outcomes would you predict? A. Pepsin would break down the protein molecules equally well in the laboratory as in the human stomach since it is a stable chemical. B. Pepsin would probably NOT break down proteins in the test tube because pepsin is designed to work at very acidic pH ranges. C. Pepsin would partially break down the protein molecules but would not work well due to the absence of DNA in the test tube. D. Pepsin would probably NOT break down proteins in the test tube because enzymes cannot exist outside of the human body.