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': 'Initial IOC for intussesception is: March 2003 \nSelect and explain. \nA. X-ray, B. USG, C. Barium enema, D. CT scan', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Ans. B i.e. USG', 'role': 'assistant'}]