Out of the given options, option 4 - Trypsin is the correct answer as it is an enzyme. An enzyme is a protein molecule that acts as a catalyst in biochemical reactions. Trypsin is a digestive enzyme that helps in the breakdown of proteins into smaller peptide chains. It is produced in the pancreas and secreted into the small intestine, where it aids in the digestion and absorption of dietary proteins.

Option 1 - Glucagon, option 2 - Insulin, and option 3 - Somatotropin are not enzymes. Glucagon is a hormone produced by the pancreas that increases blood glucose levels. Insulin is also a hormone produced by the pancreas, but it decreases blood glucose levels. Somatotropin, also known as growth hormone, is produced by the pituitary gland and plays a role in growth and metabolism.

Therefore, the correct answer is option 4 - Trypsin.