## Core Concept
The hot air oven is a type of sterilization equipment used in laboratories and medical settings to sterilize equipment and materials. It works by circulating hot air to achieve a temperature that is lethal to microorganisms. The effectiveness of sterilization depends on both the temperature achieved and the duration for which that temperature is maintained.

## Why the Correct Answer is Right
For a hot air oven set at a temperature of 160°C, the standard holding time required for effective sterilization is 45 minutes (or 1 hour for some protocols). This duration ensures that the heat penetrates through the materials being sterilized and kills all forms of microbial life. The combination of temperature and time is critical; for example, while higher temperatures might allow for shorter holding times, 160°C is commonly used with a 45-minute hold.

## Why Each Wrong Option is Incorrect
- **Option A:** Typically represents a shorter time frame that might not be sufficient for complete sterilization at the given temperature.
- **Option B:** Could represent a longer or shorter time but does not align with standard protocols for 160°C.
- **Option D:** Suggests a significantly longer time than usually required for this temperature, potentially unnecessary and less practical for routine sterilization procedures.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the validation of sterilization procedures, including those using hot air ovens, is crucial for ensuring that materials are sterile and safe for use. Different temperatures and times may be used for different types of materials, but 160°C for 45 minutes is a commonly accepted protocol.

## Correct Answer: C. 45 minutes.