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: Anatomy
[{'content': 'Vaginal sphincter is formed by all except: \nSelect and explain. \nA. Internal urethral sphincter, B. External urethral sphincter, C. Pubovaginalis, D. Pubovaginalis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A i.e. Internal urethral sphincter The musculature surrounding the internal urethral orifice of female bladder is not organized into an internal sphincter. In other words females lack internal urethral sphincterQ', 'role': 'assistant'}]