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': 'Muscle which is primarily responsible for rectal continence - \nSelect and explain. \nA. Ext. sphincter, B. Int. sphincter, C. Puborectalis, D. Sacrococcoygeous', 'role': 'user'}, {'content': 'Answer: C \nExplanation: None', 'role': 'assistant'}]