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': 'Which one of the following distinguishes ARDS (acute/adult respiratory distress syndrome) from cardiogenic pulmonary oedema ? \nSelect and explain. \nA. Normal PaO2, B. Normal pulmonary arterial pressure, C. Normal arterial-alveolar gradient, D. Normal PaCO2', 'role': 'user'}, {'content': 'Answer: B \nExplanation: None', 'role': 'assistant'}]