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: Dental
Most common cause of failure of class II restoration in
children is: 
Select and explain. 
A. Margin failure, B. Proximal box fracture, C. Inadequate width, D. Too much width
B: Proximal box fracture
Answer: B: Proximal box fracture 
Explanation: None