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
2 year old child with length 85cm and weight of 11kg was found to have serum urea of 49mg/dl, serum creatinine 2mg/dl What is the estimated GFR of this child, as per Schwartz formula? 
Select and explain. 
A. 9, B. 18, C. 48, D. 90
B: 18
Answer: B: 18 
Explanation: schwartz formula for creatinine clearance :
= k  X length / serum creatinine
( k = 0.42)
GFR = 0.42 X 85/2 = 17.8 ≈ 18.