<prompt> b - Lactam ring is present inErythromycinPenicillinTetracyclinsChloramphenicol  <response>: 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 