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': 'A criterion for the diagnosis of acute respiratory distress syndrome is? \nSelect and explain. \nA. PaO2/FiO2 >400 mm Hg, B. PaO2/FiO2 <200 mm Hg, C. PaO2/Fi02 < 300 mm Hg, D. PCWP > 18 mm Hg', 'role': 'user'}, {'content': 'Answer: B \nExplanation: ARDS is a clinical syndrome of severe dyspnea of rapid onset, hypoxaemia, and diffuse pulmonary infiltrates leading to respiratory failure. \nThe most definitive characteristic of ARDS is the arterial PaO2 (in mmHg) / FiO2(inspiratory O2 fraction) < 200 mmHg, while a PaO2/FiO2 between 200 and 300 identifies patients with acute lung injury who are likely to benefit from aggressive therapy.', 'role': 'assistant'}]