This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Developmental-Behavioral Screening and Surveillance, 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 AgeMilestone2 MonthSocial smile3 MonthRecognise mother6 MonthStmger anxiety9 Monthwave bye - bye12 MonthComes when called15 MonthJargon18 MonthsCopies parents task2 yearAsk for food, drink, shows toys3 yearKnow full name & gender4 yearPlays in group.5 yearHelps in household task, decrease & undresses", 'role': 'assistant'}]