Which one of the following is a broad spectrum antibiotic?

Auromycin (chlortetracycline) is a tetracycline-class antibiotic effective against both Gram-positive and Gram-negative bacteria, making it broad-spectrum. Penicillin G and Benzyl penicillin are narrow-spectrum, primarily effective against Gram-positive bacteria. Salicylamide is not an antibiotic but a non-steroidal anti-inflammatory drug derivative.