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': 'Invertogram to be done in a newborn – \nSelect and explain. \nA. Immediately, B. After 2 hours, C. After 4 hours, D. After 6 hours', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Invertogram is done to detect imperforate anus.\nIt is done after six hours of birth in infant as sufficient air may have collected in large intestine to cast a X-ray shadow.', 'role': 'assistant'}]