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': 'Tertiary syphilis most frequently involves the \nSelect and explain. \nA. CNS, B. Liver, C. Testes, D. Aorta', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]