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
Most severe and persistent symptom for acute mountain sickness is: 
Select and explain. 
A. Headche, B. Dizziness, C. Drowsiness, D. Cyanosis
A: Headche
Answer: A: Headche 
Explanation: 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