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: Pharmacology
[{'content': 'Intravenous regional anesthesia is suitable for : \nSelect and explain. \nA. Orthopedic manipulation on the upper limb, B. Vascular surgery on the lower limb, C. Head and neck surgery, D. Caesarian section', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]