Final answer:
The hormone that stimulates the production of RBCs is called erythropoietin (EPO), which is secreted by the kidneys in response to low oxygen levels and stimulates red blood cell production in the bone marrow.
Step-by-step explanation:
The hormone that promotes the production of RBC (Red Blood Cells) is called erythropoietin (EPO). Erythropoietin is a glycoprotein hormone that is secreted by the interstitial fibroblast cells in the kidneys. It is produced in response to low oxygen levels in the body and has the primary function of stimulating the production of red blood cells in the bone marrow. EPO facilitates the proliferation and differentiation of the erythrocyte lineage, effectively ensuring that the blood has ample red blood cells to transport oxygen throughout the body.