This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: All India exam, Subject name: Anatomy
Primitive red cells first originates in the early embryonic life is in: 
Select and explain. 
A. Liver, B. Yolk sac, C. Bone marrow, D. Spleen
B: Yolk sac
Answer: B: Yolk sac 
Explanation: During embryogenesis, hematopoiesis occurs in extraembryonic yolk sac, the fetal liver, the thymus, and the preterm marrow. The origin of hematopoietic cells is closely tied to gastrulation, the formation of mesoderm cells, and to the emergence of the endothelial lineage. ref ; BD chaurasia ,grays anatomy