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 tumor in less than 20 year age group is : \nSelect and explain. \nA. Epithelial tumour, B. Germ cell tumour, C. Metastatic tumour, D. Sexcord stromal tumour', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Germ cell tumour', 'role': 'assistant'}]