The correct answer is option 2: Thrombin. Thrombin is an enzyme that plays a key role in the process of blood clotting. When the body is injured and blood vessels are damaged, the clotting process is activated to prevent excessive bleeding. Thrombin is responsible for converting a soluble protein called fibrinogen into an insoluble protein called fibrin. Fibrin forms a mesh-like structure that traps blood cells and platelets, forming a blood clot. This clotting process is essential for wound healing and preventing further blood loss.

Option 1: Amylase is an enzyme that breaks down carbohydrates and is not involved in blood clotting.

Option 3: Pepsin is an enzyme that aids in protein digestion and is not involved in blood clotting.

Option 4: Renin is an enzyme involved in regulating blood pressure and is not involved in blood clotting.