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
Beta lactam antibiotics are all except : 
Select and explain. 
A. Amoxicillin, B. Aztreonam, C. Ceftriaxone, D. Vancomycin
D: Vancomycin
Answer: D: Vancomycin 
Explanation: None