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': 'A criterion for diagnosis of acute respiratory distress syndrome is? \nSelect and explain. \nA. PaO2/FiO2 >400 mm Hg, B. Slow onset dyspnea, C. PaO2/FiO2 <_200 mm Hg, D. PCWP>l8 mm Hg', 'role': 'user'}, {'content': "Answer: C \nExplanation: ARDS is a clinical syndrome of severe dyspnoea of rapid onset,hypoxaemia,and diffuse pulmonary infiltrates leading to respiratory failure.The most definitive characteristic of ARDS is the aerial Po2 (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. Reference:Harrison's Medicine-20th edition,page no:2032", 'role': 'assistant'}]