**Core Concept:** Sterilization is the process of destroying microorganisms from a substance to ensure its safety for medical use. Liquid paraffin, also known as petroleum jelly, is often used as a vehicle for topical medications. Sterilization methods aim to inactivate microorganisms without affecting the properties of the substance.

**Why the Correct Answer is Right:** Sterilization of liquid paraffin is done by heating it to a high temperature, typically around 160°C (320°F). This high temperature kills microorganisms effectively without altering the consistency or quality of the paraffin.

**Why Each Wrong Option is Incorrect:**

A. Boiling point of liquid paraffin is about 71°C (160°F), making this option insufficient to kill microorganisms effectively.
B. Sterilization by cooling the paraffin, such as by freezing, is inadequate as it fails to eliminate microorganisms.
C. Using light sources like ultraviolet (UV) or gamma radiation does not sterilize liquid paraffin, as these methods may not penetrate the thick consistency of the paraffin, allowing microorganisms to remain alive.
D. Sterilization by adding chemical agents like chemicals or bleach is not suitable for paraffin sterilization due to the risk of chemical contamination or altering the paraffin's properties.

**Clinical Pearl:** Sterilization of liquid paraffin is essential for ensuring patient safety when used in medical settings. Achieving this involves heating the paraffin to a high temperature (≈160°C or 320°F) and maintaining it at that temperature for a sufficient duration to inactivate microorganisms without compromising the substance's quality.