The enzyme pepsin is produced in the cells of the stomach but not in the cells of the small intestine. The small intestine produces a different enzyme, trypsin. The reason that the stomach and small intestine produce different enzymes is that the gene that codes for pepsin is A) in the cells of the stomach, but not in the cells of the small intestine B) mutated in the small intestine C) digested by the trypsin in the small intestine D) expressed in the stomach but not expressed in the small intestine