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': 'Not a histological marker for choriocarcinoma: \nSelect and explain. \nA. Vill, B. Cytotrophoblast, C. Syncytiotrophoblast, D. Bizarre nuclei', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Vill', 'role': 'assistant'}]