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
[{'content': 'Most common site of thrombosis in paroxysmal nocturnal hemoglobinuria \nSelect and explain. \nA. Femoral vein, B. Median cubital vein, C. Intra - abdominal veins, D. Saphenous vein', 'role': 'user'}, {'content': 'Answer: C \nExplanation: Intra abdominal veins are the most common site of thrombosis in PNH.', 'role': 'assistant'}]