This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: general microbiology, Subject name: Microbiology
b - Lactam ring is present in 
Select and explain. 
A. Erythromycin, B. Penicillin, C. Tetracyclins, D. Chloramphenicol
B: Penicillin
Answer: B: Penicillin 
Explanation: All penicillins have the basic structure. A thiazolidine ring (A) is attached to a b-lactam ring (B) that carries a secondary amino group (RNH-).Reference: Katzung&;s Pharmacology; 13th edition; Chapter 43; Beta-Lactam & Other Cell Wall- & Membrane-Active Antibiotics