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
Nosocomial pneumonia is most commonly caused by 
Select and explain. 
A. Gram -ve bacilli, B. Gram + ve bacilli, C. Gram - ve cocci, D. Mycoplasma
A: Gram -ve bacilli
Answer: A: Gram -ve bacilli 
Explanation: None