This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pediatrics
Child knows his/her sex by age of? 
Select and explain. 
A. 2 year, B. 3 year, C. 4 year, D. 5 year
B: 3 year
Answer: B: 3 year 
Explanation: Ans. is 'b' i.e., 3 year