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
[{'content': 'Which of the following is seen in high attitude climbers: \nSelect and explain. \nA. Hyperventilation, B. Hyperventilation, C. Pulmonary edema, D. All', 'role': 'user'}, {'content': 'Answer: D \nExplanation: A i.e. Hyperventilation, (B) i.e. Decreased Pa CO2 (C) pulmonary edema', 'role': 'assistant'}]