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
Commonest complication following haemorrhoidectomy is - 
Select and explain. 
A. Hemorrhage, B. Infection, C. Facal impaction, D. Urinary Retention
D: Urinary Retention
Answer: D: Urinary Retention 
Explanation: None