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: Medicine
Most common cause of Budd Chiari syndrome is - 
Select and explain. 
A. Idiopathic, B. Valves in hepatic veins, C. Hepatocellular carcinoma, D. Thrombosis of hepatic veins
D: Thrombosis of hepatic veins
Answer: D: Thrombosis of hepatic veins 
Explanation: None