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
This milestone develops at age of ________
assistant
The correct answer is  At 4 months Lifts head and chest, with head in an approximately veical axis. legs extended Reaches and grasps objects and brings them to mouth Enjoys sitting with full trunkal suppo When held erect pushes with feet Laughs out loud Excites at sight of food Ref : Nelson 20th edit pg:67