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: Surgery
[{'content': "Buerger's angle that indicates severe ischaemia is \nSelect and explain. \nA. 120°, B. 80°, C. 60°, D. 30°", 'role': 'user'}, {'content': "Answer: D \nExplanation: If Buerger's angle is < 30°, it indicates severe ischaemia.", 'role': 'assistant'}]