This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Radiology
[{'content': 'The best method of investigation is case of acute cholecystitis is \nSelect and explain. \nA. Ultrasound, B. ERCP, C. OCG, D. Radionuclide imaging', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Radionuclide imaging', 'role': 'assistant'}]