The correct option is C Erythropoietin
Erythropoiesis is the process, which produces red blood cells. It is stimulated by decreased oxygen in circulation, which is detected by kidneys which then secretes the hormone erythopoietin. This hormone stimulates proliferation and differentiation of the red blood cell precursors. When there is anemia, there is low oxygen tension in the body. Because of this, there is a rise in the cell count due to liberation of erythropoietin.
Thus, the correct answer is option (C), 'Erythropoietin'.