The correct option is C Junction of hepato-pancreatic duct and duodenum
Opening of the hepato-pancreatic duct into the duodenum is guarded by a sphincter of Oddi.
The opening of ileum into caecum is guraded by the ileo-caecal valve.
The undigested food enters into the caecum of the large intestine through an ileo-caecal valve, which prevents the backflow of the faecal matter.
At the gastro-oesophageal junction, there is a gastro-oesophageal sphincter that controls the passage of food into the stomach.