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': 'Most common investigation done for obstructive jaundice – \nSelect and explain. \nA. CT scan, B. USG, C. X-ray, D. ERCP', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]