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': "Singnet ring in an ovarian tumour is characteristic of : \nSelect and explain. \nA. Krukenberg's tumour, B. Dysgerminoma, C. Granulosa cell carcinoma, D. Papillary cysatadenocarcinoma", 'role': 'user'}, {'content': "Answer: A \nExplanation: Krukenberg's tumour", 'role': 'assistant'}]