This drug has activity against many strains of Pseudomomas aeruginosa. However, when it is used alone, resistance has emerged during the course of treatment. The drug should not be used in penicillinallergic patients. Its activity against gramnegative rods is enhanced if it is given in combination with tazobactam (a) Amoxicillin (b) Aztreonam (c) Imipenem (d) Piperacillin (e) Vancomycin