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': 'Most common ovarian tumour in less than 20 year old is: \nSelect and explain. \nA. Epithelial tumour, B. Germ cell tumour, C. Metastatic tumour, D. Sex cord stromal tumour', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Below 20 years, 60% ovarian tumours are of germ cell origin and in girls less than 105, 85% tumours are of germ cell origin. Ref: Shaw 15th edition: page; 376.', 'role': 'assistant'}]