Initial site of RBC production in fetus-

Ans. is 'b' i.e., Yolk sac* Embryonic and fetal hematopoiesis occurs in three phases: megaloblastic, hepatic, and myeloid. At each phase of RBC development both the sites of production and the cell composition change.* Sites and stages of fetal erythropoiesis: Primitive erythropoiesis begins in the yolk sac at 2 to 3 weeks after conception. By the end of the first trimester, the liver has become the main erythroid organ. The liver is the primary source of red blood cells during the second trimester, and the bone marrow is the primary source of red blood cells during the last trimester