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
[{'content': 'The commonest cause of an obliterative stricture of the membranous urethra is - \nSelect and explain. \nA. Fall-astride injury, B. Road-traffic accident with fracture pelvis and rupture urethra, C. Prolonged catheterization, D. Gonococcal infection', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Commonest cause of stricture in posterior urethra → Trauma with fracture pelvis\nCommonest cause of stricture in anterior urethra → Straddle injuries (direct trauma to the perineal region).', 'role': 'assistant'}]