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': 'Oogonia are derived from : \nSelect and explain. \nA. Amnion, B. Yolk sac, C. Stroma of ovary, D. Germinal epithelium', 'role': 'user'}, {'content': 'Answer: B \nExplanation: Yolk sac', 'role': 'assistant'}]