This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Bile duct, Subject name: Surgery
[{'content': 'Most common surgical cause of obstructive jaundice: \nSelect and explain. \nA. Periampullary carcinoma, B. Carcinoma gallbladder, C. Carcinoma head of pancreas, D. CBD stone', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Obstructive Jaundice MC surgical cause of obstructive jaundice is CBD stones Characterized by dark urine, clay colored stools, icterus and pruritus Presence of urobilinogen in urine rules out obstructive jaundice USG is the best test to differentiate medical from surgical jaundice.', 'role': 'assistant'}]