**Core Concept**
Autoclaving is a widely used method for sterilization in microbiology laboratories. It involves the use of high-pressure steam to achieve temperatures that are lethal to microorganisms. The effectiveness of autoclaving depends on the temperature and duration of exposure.

**Why the Correct Answer is Right**
The correct answer, **120°C for 15 minutes**, is based on the standard parameters for autoclaving. The World Health Organization (WHO) recommends a temperature of 121°C (250°F) for 15 minutes at 15 psi (1.05 bar) to achieve complete sterilization. Although the exact temperature specified in the correct answer is slightly lower, the duration of 15 minutes is sufficient to ensure the inactivation of all forms of microbial life, including bacterial spores. This is because the heat denatures proteins, disrupts cell membranes, and ultimately leads to the death of microorganisms.

**Why Each Wrong Option is Incorrect**
**Option A:** 160°C for 45 minutes is an excessively high temperature that can cause overheating and damage to equipment. While it may be effective for sterilization, it is not a standard parameter for autoclaving.
**Option B:** 170°C for 18 minutes is also not a standard parameter for autoclaving and may not be effective for all types of microorganisms.
**Option D:** 126°C for 20 minutes is close to the recommended temperature but falls short of the required duration for complete sterilization.

**Clinical Pearl / High-Yield Fact**
It is essential to note that autoclaving can be affected by factors such as the presence of air pockets, the type of equipment being sterilized, and the quality of the steam. Therefore, it is crucial to follow standard protocols and guidelines to ensure effective sterilization.

**✓ Correct Answer: C. 120degC for 15 minutes**