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
Which among the following is not a beta lactamase resistant Penicillin? 
Select and explain. 
A. Methicillin, B. Carbenicillin, C. Nafcillin, D. Oxacillin
B: Carbenicillin
Answer: B: Carbenicillin 
Explanation: Ans. is 'b' i.e., Carbenicillin