This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Growth and development, Subject name: Pediatrics
This milestone is achieved by the age of _________ 
Select and explain. 
A. 2 months, B. 4 months, C. 6 months, D. 8 months
B: 4 months
Answer: B: 4 months 
Explanation: 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 edition pg:67