This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.V.S., Subject name: Pediatrics
Which of the following is the major site of erythropoietin production during the fetal stage: 
Select and explain. 
A. Liver, B. Yolk, C. Bone, D. Spleen
A: Liver
Answer: A: Liver 
Explanation: a. Liver(Ref: Nelson's 20/e p 2306)Erythropoietin (EPO) is produced in fetal liver during 1st & 2nd trimesters, by cells of monocyte/macrophage origin.After birth, the anatomic site of EPO production shifts to the kidney.