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': 'The most common cause of superficial throm-bophlebitis is \nSelect and explain. \nA. Intravenous catheters / infusion, B. DVT, C. Varicose veins, D. Trauma', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]