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
Primary bone graft in cleft palate patient? 
Select and explain. 
A. 6 month - 1 year, B. < 2 year, C. 2-4 year, D. 4-5 year
B: < 2 year
Answer: B: < 2 year 
Explanation: None