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: Medicine
[{'content': 'Reversible airway obstruction is defined as ___ percentage increase in FEV1, 15 minutes after an inhaled sho-acting beta 2 -agonist therapy- \nSelect and explain. \nA. >_ 5%, B. >_10, C. >_ 15%, D. >_ 20', 'role': 'user'}, {'content': "Answer: C \nExplanation: Diagnosis of reversible airway obstruction or asthma is made when FEV1 >/= 15% (and 200 ml) increase following administration of a bronchodilator ,like sho acting beta2 agonists, or trial of coicosteroids.It can also be diagnosed as >20% diurnal variation on >/= 3 days in a week for 2 weeks on PEF diary & FEV1 >/= 15% decrease after 6 mins of exercise. Reference:Davidson's medicine-22nd edition,page no:668/", 'role': 'assistant'}]