The correct option is
C Pancreas
Secretin is a hormone that regulates water homeostasis. It is secreted by the duodenum. When hydrochloric acid passes from the stomach into the duodenum, secretin is released. It stimulates the acinar cells of the pancreas to secrete water and bicarbonate into the pancreatic duct. This water and bicarbonate is then drained into the duodenum.
Thus, the correct answer is 'Pancreas.'