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': 'Drug of choice for deep vein thrombosis prophylaxis in surgical patients is : \nSelect and explain. \nA. Intravenous unfractionated heparin, B. Subcutaneous unfractionated heparin, C. Subcutaneous low molecular weight heparin, D. Warfarin', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]