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
Oogonia are derived from : 
Select and explain. 
A. Amnion, B. Yolk sac, C. Stroma of ovary, D. Germinal epithelium
B: Yolk sac
Answer: B: Yolk sac 
Explanation: Yolk sac