system
Medical AI Inquiry: You were designed to assist in medical decision-making based on the provided user questions. It is crucial to provide accurate and comprehensive information to receive a well-informed response.
user
Child knows his/her sex by age of-
assistant
The correct answer is  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