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: Surgery
The neonatal kidney achieves concentrating ability equivalent to adult's kidney by ? 
Select and explain. 
A. One year of age, B. Eighteen months of age, C. Three to six months of age, D. Just before pubey
A: One year of age
Answer: A: One year of age 
Explanation: Ans. is 'a' i.e., One year of age