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: Pediatrics
[{'content': 'Child knows his/her sex by age of? \nSelect and explain. \nA. 2 year, B. 3 year, C. 4 year, D. 5 year', 'role': 'user'}, {'content': "Answer: B \nExplanation: Ans. is 'b' i.e., 3 year", 'role': 'assistant'}]