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: Gynaecology & Obstetrics
[{'content': 'Tumor marker for choriocarcinoma : \nSelect and explain. \nA. HCG, B. AFP, C. CEA, D. Desmin', 'role': 'user'}, {'content': 'Answer: A \nExplanation: HCG', 'role': 'assistant'}]