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: Physiology
Erythropoietin level are increased by - 
Select and explain. 
A. ↓PO2, B. ↓PCO2, C. ↓Hb, D. ↓pH
A: ↓PO2
Answer: A: ↓PO2 
Explanation: Hypoxia stimulates the release of Erythropoietin.