This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Pelvis and Perineum 3, Subject name: Anatomy
[{'content': 'While a patient was being given an obstetric nerve block she gradually lost her voluntary control over urination. The muscle which got anaesthetized is located in the \nSelect and explain. \nA. Trigone of the bladder, B. Urogenital diaphragm, C. Superficial perineal pouch, D. Pelvic diaphragm', 'role': 'user'}, {'content': 'Answer: B \nExplanation: The urogenital diaphragm contains the external urinary sphincter & deep transversus perinei muscle which is responsible for voluntary control over urination. In its blockade, the voluntary control over micturition will be lost.', 'role': 'assistant'}]