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
Delayed union of fracture of a bone follo-wing a surgical treatment may be due to 
Select and explain. 
A. Infection, B. Inadequate circulation, C. Inadequate mobilization, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: D i.e. All