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': 'Commonest malignancy of ovary is : \nSelect and explain. \nA. Serous type, B. Mucinous, C. Dermoid cyst, D. Granulosa cell tumour', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Serous type', 'role': 'assistant'}]