This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
[{'content': 'For development of alveolar PO2 of 60 mm Hg and high altitude illness to develop in an otherwise healthy person from sea level, rapid ascent to following height is required \nSelect and explain. \nA. 2,000 meters, B. 3,000 meters, C. 4,000 meters, D. 5,000 meters', 'role': 'user'}, {'content': 'Answer: B \nExplanation: People have different susceptible to altitude sickness,on an average it begins around 2000 to 3000 meters above sea level Ref:Guyton and Hall textbook of medical physiology 12th edition,page number:375,376', 'role': 'assistant'}]