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': 'A patient with external hemorrhoids develops pain while passing stools. The nerve mediating this pain is - \nSelect and explain. \nA. Hypogastric nerve, B. Pudendal nerve, C. Splachnic visceral nerve, D. Sympathetic plexus', 'role': 'user'}, {'content': 'Answer: B \nExplanation: External piles (hemorrhoids) lie below the pectinate line and are therefore painful.\nPain sensation below the pectinate line is carried by inferior rectal nerve, a branch of the pudendal nerve.', 'role': 'assistant'}]