Which of the following is a common cause of pancreatitis?

Gallstones are a common cause of pancreatitis because they can block the pancreatic duct, preventing enzymes produced by the pancreas from flowing into the small intestine. Instead, these enzymes can begin to digest the pancreas itself, leading to inflammation known as pancreatitis. This blockage can occur when a gallstone passes out of the gallbladder and into the common bile duct, where it can interfere with the normal flow of pancreatic juices.

Other potential causes of pancreatitis can include excessive alcohol consumption and certain medications, but among the options listed, gallstones are particularly significant due to their direct mechanism of causing the condition through obstruction.