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': 'Bleeding vessel in haemorrhoids is \nSelect and explain. \nA. Superior rectal aery, B. Superior rectal vein, C. Middle rectal aery, D. Middle rectal vein', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Bleeding vessel in haemorrhoids is superior rectal vein which is a branch of inferior mesenteric vein at the level of rectum. Dilation of these vessels leads to bleeding leading to internal haemorrhoids. Veins are better option than aery.', 'role': 'assistant'}]