Drug of choice for anaerobic infection is

Ans. is 'b' i.e., Metronidazole * Metronidazole is a prototype nitroimidazole which has broad spectrum cidal activity against the anaerobic micro-organisms including giardia lamblia.* It doesn't affect the aerobic bacteria.* It is selectively toxic to anaerobic and micro-aerophilic micro-organisms.* In anerobic conditions, it produces highly cytotoxic nitro radical which is attenuated in aerobic environment.* It also induces mutagenesis and cause radiosensitization.* Aminoglycosides are active only against aerobes.* Amphotericin B is an anti-fungal agent.