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: Surgery
[{'content': "Investigation of choice forF'acute appendicitis in children: \nSelect and explain. \nA. CT scan, B. Ultrasound, C. MRI, D. X-ray", 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. b. Ultrasound', 'role': 'assistant'}]