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: Pathology
Normal amount of pleural fluid is approximately 
Select and explain. 
A. 5ml, B. 15 ml, C. 50 mL, D. 100m1
B: 15 ml
Answer: B: 15 ml 
Explanation: Normally, no more than 15 ml of serous, relatively acellular, clear fluid lubricates the pleural surface.
Increased accumulation of pleural fluid is called pleural effusion