This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anticoagulants and Coagulants, Subject name: Pharmacology
[{'content': 'All the following drugs are used for thrombo prophylaxis except \nSelect and explain. \nA. Heparin, B. Warfarin, C. Aspirin, D. Anti thrombin', 'role': 'user'}, {'content': "Answer: D \nExplanation: Ans is 'd' i.e. Anti thrombin", 'role': 'assistant'}]