All have beta lactam ring EXCEPT -: (A) Penicillin, (B) Linezolid, (C) Cefotaxime, (D) Imipenem
Answer is B. Ans. is 'b' i.e., Linezolid beta-lactam antibiotics contain beta-lactam ring. These are penicillins, cephalosporins (e.g. cefotoxime), monobactams (aztreonam) and carbapenems (imipenem, meropenem).