The correct option is A Both Assertion and Reason are correct and Reason is the correct explanation for Assertion
Erythropoietin is a hormone released by the kidney that increases the RBC production. When the RBC levels are low, the kidney is stimulated to release erythropoietin into the blood which reaches bone marrow. It acts on the hemopoietic stem cells to increase the RBC production. So, the correct option is B.