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': 'Arterial thrombosis is seen in \nSelect and explain. \nA. Homocysteinemia, B. Protein S deficiency, C. Protein C deficiency, D. Antithrombin III deficiency', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]