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
mental retardation can be proved if delayed milestones and slow or retarded growth seen upto which age (in year)? 
Select and explain. 
A. 12, B. 16, C. 18, D. 20
C: 18
Answer: C: 18 
Explanation: Ans. is 'c' i.e., 18 year