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 site of thrombosis in paroxysmal nocturnal hemoglobinuria 
Select and explain. 
A. Femoral vein, B. Median cubital vein, C. Intra - abdominal veins, D. Saphenous vein
C: Intra - abdominal veins
Answer: C: Intra - abdominal veins 
Explanation: Intra abdominal veins are the most common site of thrombosis in PNH.