This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Aerial disorders, Subject name: Surgery
[{'content': 'Definition of critical limb ischemia includes:- \nSelect and explain. \nA. Rest/Night pain, B. Ankle blood pressure >50 mm Hg, C. Intermittent claudication, D. Well preserved tissues', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Critical limb Ischemia CLI results from severe aerial occlusive disease in whom resting blood flow cannot provide for basal nutritional needs of tissues Ischemic symptoms are present even during rest (rest pain) Pain is worse when legs are horizontal and may improve when legs are kept in a dependent position. Ischemic ulcers, lesions on the foot and gangrene may be seen ABI < 0.5', 'role': 'assistant'}]