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
Following acute respiratory response to ascent to high altitude, there is normalization of blood pH.The mechanism is 
Select and explain. 
A. Increased erythropoiesis leads to increased buffering by haemoglobin, B. Increased excretion of HCO3– by the kidneys, C. Increased levels of 2, 3–DPG, D. Retention of bicarbonate by the kidneys
B: Increased excretion of HCO3– by the kidneys
Answer: B: Increased excretion of HCO3– by the kidneys 
Explanation: Decrease in PaO2 stimulates the peripheral chemoreceptors at high altitudes. This triggers hyperventilation. Hyperventilation results in CO2 washout and respiratory alkalosis. This is compensated by increased excretion of bicarbonates by the kidney.