This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Abdomen and pelvis, Subject name: Anatomy
[{'content': 'Tone of the anal sphincter in maintained by \nSelect and explain. \nA. Nervi erigentes, B. Inferior hypogastric plexus, C. Inferior rectal nerve, D. Pelvic splanchnic nerves', 'role': 'user'}, {'content': 'Answer: C \nExplanation: The anal sphincters and puborectalis are the primary muscles responsible for continence. There are two sphincters: the internal anal sphincter, and the external anal sphincter. The internal sphincter is responsible for 85% of the resting muscle tone and is involuntary. ref - BDC 6e vol2 pg413-416', 'role': 'assistant'}]