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
All the following drugs are used for thrombo prophylaxis except 
Select and explain. 
A. Heparin, B. Warfarin, C. Aspirin, D. Anti thrombin
D: Anti thrombin
Answer: D: Anti thrombin 
Explanation: Ans is 'd' i.e. Anti thrombin