This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Anaemia in Pregnancy, Subject name: Gynaecology & Obstetrics
Initial site of RBC production in fetus 
Select and explain. 
A. Gestational sac, B. Yolk sac, C. Placenta, D. Fetal bones
B: Yolk sac
Answer: B: Yolk sac 
Explanation: Hematopoiesis - 1st demonstrable in yolk sac followed by liver and then finally spleen and bone marrow life span of fetal RBCs at term - 90 days