This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdominal Radiography, Subject name: Radiology
[{'content': 'Linear filling defect on ERCP is characteristic of - \nSelect and explain. \nA. Bile duct stone, B. Pancreatic duct stone, C. Worm in biliary tree, D. Stricture', 'role': 'user'}, {'content': "Answer: C \nExplanation: Ans. is 'c' i.e., Worm in biliary tree Imaging in ascariasiso Plain abdominal X ray: calcified worm,o USG: moving echogenic structures or strips,o ERCP: linear filling defect.", 'role': 'assistant'}]