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
For prophylaxis of deep vein thrombosis used is ? 
Select and explain. 
A. Warfarin, B. Heparin, C. Pneumatic shocks garment, D. Graded stocking
B: Heparin
Answer: B: Heparin 
Explanation: Answer is 'b' i.e. Heparin