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
Most common cause of empyema is - 
Select and explain. 
A. Bronchopleural fistula, B. Tubercular pneumonia, C. Bacterial pneumonia, D. Pleurisy
C: Bacterial pneumonia
Answer: C: Bacterial pneumonia 
Explanation: None