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: Pathology
[{'content': 'Stasis as a cause of thrombosis is important in: \nSelect and explain. \nA. Sickle cell Anemia, B. Venous circulation, C. Polycythemia, D. All of the above', 'role': 'user'}, {'content': 'Answer: D \nExplanation: None', 'role': 'assistant'}]