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: Medicine
[{'content': 'Most severe and persistent symptom for acute mountain sickness is: \nSelect and explain. \nA. Headche, B. Dizziness, C. Drowsiness, D. Cyanosis', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Ans. A: HeadcheHeadaches are the primary symptom used to diagnose altitude sickness, although a headache is also a symptom of dehydration.A headache occurring at an altitude above 2,400 metres (8000 feet = 76 kPa), combined with any one or more of the following symptoms, may indicate altitude sickness:Lack of appetite, nausea, or vomitingFatigue or weaknessDizziness or light-headednessInsomniaPins and needlesShoness of breath upon exeion', 'role': 'assistant'}]