Final answer:
Activation of the pancreatic proteases occurs in the duodenum to prevent self-digestion of the pancreas. Enzymes like enteropeptidase in the duodenum activate the proteolytic enzymes secreted by the pancreas.
Step-by-step explanation:
To prevent self-digestion of the pancreas, activation of pancreatic proteases occurs in the duodenum. This is crucial because if these enzymes were activated inside the pancreas, they would start digesting the organ itself, leading to a condition known as pancreatitis. Pancreatic proteases are produced in inactive forms and are then activated in the duodenum where they can safely digest proteins in the food we eat. The important enzyme enteropeptidase converts trypsinogen to trypsin, which in turn activates other proteolytic enzymes such as procarboxypeptidase and chymotrypsinogen into carboxypeptidase and chymotrypsin respectively.
The pancreas is where most fat-digesting enzymes, such as lipases, are produced. These enzymes are delivered to the duodenum along with bicarbonate to neutralize the acidic chyme from the stomach and aid in the digestion of fats, proteins, and carbohydrates. Hence, the correct direct answer to the question is 'A. duodenum'.