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': 'Best investigation in acute cholecystitis is: \nSelect and explain. \nA. Technetium scan, B. HIDA scan, C. Pipida scan, D. Plain X-ray abdomen', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. HIDA scan', 'role': 'assistant'}]