This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Respiratory system, Subject name: Physiology
The stimulation of which of the following causes hyperventilation at high altitude 
Select and explain. 
A. Peripheral chemoreceptors, B. Vagal afferents, C. Central chemoreceptors, D. Proprioceptors
A: Peripheral chemoreceptors
Answer: A: Peripheral chemoreceptors 
Explanation: The composition of air stays the same, but the total barometric pressure falls with increasing altitude. Therefore, the PO2 also falls. At 3000 m (approximately 10,000 ft) above sea level, the alveolar PO2 is about 60 mm Hg and there is enough hypoxic stimulation of the peripheral chemoreceptors to definitely increase ventilation. As one ascends higher, the alveolar PO2 falls less rapidly and the alveolar PCO2 declines somewhat because of the hyperventilation. The resulting fall in aerial PCO2 produces respiratory alkaloids.Ref: Ganong review of medical physiology 23rd edition Page no: 617