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: Unknown
[{'content': 'Object permanence in a child is seen after: \nSelect and explain. \nA. 6 months, B. 9 months, C. 12 months, D. 15 months', 'role': 'user'}, {'content': 'Answer: A \nExplanation: (Refer: Nelson’s Textbook of Pediatrics, 19th edition, chapter 8th, 9th and 10th)\nMilestones', 'role': 'assistant'}]