**Core Concept**
A hot air oven is a type of physical sterilization method that utilizes dry heat to eliminate microorganisms. This process is effective for sterilizing heat-stable equipment and supplies, particularly those that cannot be exposed to moisture or steam.

**Why the Correct Answer is Right**
Hot air ovens operate by circulating hot air at a temperature of 170-190°C (338-374°F) for a specified period, typically 1-2 hours. This dry heat method is effective against a wide range of microorganisms, including bacteria, viruses, and fungi. The high temperature denatures proteins, disrupts cellular membranes, and ultimately leads to the death of microorganisms. The dry heat also prevents the growth of thermophilic bacteria that can survive in moist environments.

**Why Each Wrong Option is Incorrect**
* **Option A:** Autoclaving is a method of sterilization that uses high-pressure steam, which is not applicable to hot air ovens.
* **Option B:** Ethylene oxide sterilization is a chemical method used for heat-sensitive equipment, not hot air ovens.
* **Option C:** Glutaraldehyde is a disinfectant used for equipment that cannot be sterilized, not a method of sterilization itself.

**Clinical Pearl / High-Yield Fact**
When using hot air ovens for sterilization, it is essential to ensure that the equipment is properly calibrated and the temperature is consistently maintained within the specified range to achieve effective sterilization.

**Correct Answer: D. Equipment and supplies that cannot be exposed to moisture or steam.**