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: Surgery
[{'content': '_______________ of Fluid is required to produce costophrenic angle bluting** on erect chest X-ray, in cases of pleural effusion: \nSelect and explain. \nA. 100ml, B. 300ml, C. 500ml, D. 750ml', 'role': 'user'}, {'content': 'Answer: B \nExplanation: At least 100ml of fluid is required to detect by USG.\nA minimum of 300ml is required to produce bluttening of costophrenic angle on erect chest X-ray.\nAbout 500ml of effusion is required for detection on clinical examination.', 'role': 'assistant'}]