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': 'Which ovarian tumor is likely to involve the opposite ovary by metastasis: \nSelect and explain. \nA. Granulosa cell tumor, B. Dysgerminoma, C. Gynandroblastoma, D. Endodermal sinus tumor', 'role': 'user'}, {'content': 'Answer: A \nExplanation: None', 'role': 'assistant'}]