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': 'Feature of exudates pleural effusion is \nSelect and explain. \nA. Pleural fluid protein: Serum protein ratio> 0.5, B. Pleural fluid protein: Serum protein ratio> 0.8, C. Pleural fluid protein: Serum protein ratio<0.5, D. Pleural fluid protein: Serum protein ratio> 1.0', 'role': 'user'}, {'content': "Answer: A \nExplanation: According to Light's criteria for distinguishing pleural transudate from exudate,exudate is likely if one or more of the following criteria are met-Pleural fluid protein:serum protein ratio>0.5;Pleural fluid LDH:serum LDH ratio>0.6;Pleural fluid LDH>2/3 rds of the upper limit of normal serum LDH. Reference:Davidson's medicine-22nd edition,page no:662.", 'role': 'assistant'}]