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: Radiology
[{'content': 'Pleural effusion can be detected clinically when the amount of fluid is more than: March 2004 \nSelect and explain. \nA. 200 ml, B. 300 ml, C. 400 ml, D. 500 ml', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Ans. D i.e. 500 ml', 'role': 'assistant'}]