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'}]