Culture media is sterilized by which of the following method?
Correct Answer: A
Rationale: Sterilization of culture media is critical in microbiology to eliminate contaminants. Autoclaving (choice A) uses moist heat under pressure (typically 121°C at 15 psi for 15-20 minutes) to kill bacteria, spores, and viruses, making it the gold standard for sterilizing liquid media like agar or broth. Boiling (choice B) at 100°C can kill vegetative bacteria but not heat-resistant spores, rendering it inadequate for complete sterilization. Hot air oven (choice C) employs dry heat (160-170°C for 2 hours) and is suitable for glassware, not liquid media, as it may evaporate or degrade nutrients. Ionizing radiation (choice D) is effective for heat-sensitive materials (e.g., plastics), but it's less common for routine media preparation due to cost and equipment needs. Autoclaving is the correct answer (A) because it ensures thorough sterilization of culture media, a process nurses and lab personnel rely on to maintain aseptic conditions for accurate diagnostic cultures.