<prompt> During first 3-4 month of gestation erythrocytes are formed byYolk sacYolk sacSpleenAll  <response>: A i.e. Yolk sac; B i.e. Liver; C i.e. Spleen Erythropoiesis blood production occurs in mesodermal wall of yolk sacQ i.e. intravascular from 3 weeks to 3 months of gestation and in liver spleen lymph nodesQ hepatic extramedullary from 2 months to 7 months of gestation. After this erythropoiesis occurs in marrow myeloid tissue. 