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': 'The Poal vein is formed: \nSelect and explain. \nA. By the superior mesenteric vein, B. By the splenic vein, C. At the level of 2nd lumbar veebra, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: All of the above', 'role': 'assistant'}]