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: Pharmacology
Penicillins are NOT effective against 
Select and explain. 
A. Gram positive cocci, B. Gram negative cocci, C. Gram positive bacilli, D. Gram negative bacilli
D: Gram negative bacilli
Answer: D: Gram negative bacilli 
Explanation: None