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
Most common cause of umbilicus does not separate at age of 2 years - 
Select and explain. 
A. Raspbery tumour, B. Leukocyte adhesion deficiency, C. Patent urachus, D. Umblical granuloma
B: Leukocyte adhesion deficiency
Answer: B: Leukocyte adhesion deficiency 
Explanation: None