This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pathology
Erythropoietin can be produced by : 
Select and explain. 
A. Brain, B. Kidney, C. Bone marrow, D. Adipose tissue
B: Kidney
Answer: B: Kidney 
Explanation: Erythropoietin is a glycoprotein hormone, produced by the kidney, which increases erythropoietic activity. The production of erythropoietin is increased in response to reduced oxygen tension in the blood reaching the kidney. It results in an increase in the number of cells committed to the erythroid line, reduced maturation time and early release of erythrocytes from the bone marrow. Erythropoietin mediates the physiological response of the bone marrow to anemia or hypoxia.