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': 'All except one describes critical limb ischaemia \nSelect and explain. \nA. ABPI = 0.3, B. Ankle SBP < 50 mmHg, C. Toe SBP < 30 mmHg, D. Ankle SBP > 30 mmHg', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ankle SBP < 50 mmHg describes critical limb ischaemia.', 'role': 'assistant'}]