<prompt> Please answer with one of the option in the bracket. Write reasoning in between . Write answer in between .Q:A 56-year-old woman presents to the emergency department with an episode of nausea and severe unrelenting right upper abdominal pain. She had a cholecystectomy for gallstones a year earlier and has since experienced frequent recurrences of abdominal pain, most often after a meal. Her past medical history is otherwise unremarkable and she only takes medications for her pain when it becomes intolerable. Her physical exam is normal except for an intense abdominal pain upon deep palpation of her right upper quadrant. Her laboratory values are unremarkable with the exception of a mildly elevated alkaline phosphatase, amylase, and lipase. Her abdominal ultrasound shows a slightly enlarged common bile duct at 8 mm in diameter N up to 6 mm and a normal pancreatic duct. The patient is referred to a gastroenterology service for an ERCP endoscopic retrograde cholangiopancreatography to stent her common bile duct. During the procedure the sphincter at the entrance to the duct is constricted. Which statement best describes the regulation of the function of the sphincter which is hampering the cannulation of the pancreatic duct in this patient?? A: A hormone released by the I cells of the duodenum in the presence of fatty acids is the most effective cause of relaxation., B: The sphincter is contracted between meals., C: Sphincter relaxation is enhanced via stimulation of opioid receptors., D: A hormone released by the M cells of the duodenum is the most effective cause of relaxation., E: Regulation of function of the sphincter of Oddi does not involve neural inputs.,  <response>: This is a medical question asking about the regulation of the sphincter of Oddi, which controls the flow of bile and pancreatic juice into the duodenum. The question provides a clinical vignette about a 56-year-old woman with post-cholecystectomy pain likely due to sphincter of Oddi dysfunction leading to an ERCP procedure. During the ERCP, the sphincter is constricted making cannulation difficult. The choices describe different mechanisms that could cause relaxation of the sphincter to allow cannulation. To answer this, I need to recall the physiology of sphincter of Oddi regulation and identify the most important regulator of sphincter relaxation.A: A hormone released by the I cells of the duodenum in the presence of fatty acids is the most effective cause of relaxation. 