This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Growth, Development, and Behavior, Subject name: Pediatrics
A child can wave "bye-bye" by what age: 
Select and explain. 
A. 6 months, B. 9 months, C. 12 months, D. 18 months
B: 9 months
Answer: B: 9 months 
Explanation: Ans. B. 9 monthsKey social and adaptive milestones2 months Social smile3 months Recognizes mother6 months:- Recognizes strangers9 months:- Waves "bye-bye"