**Core Concept**
The question requires knowledge of methods to sterilize sputum, which is crucial in microbiological and pathological analysis to prevent contamination and ensure accurate results.

**Why the Correct Answer is Right**
Sputum can be sterilized using autoclaving, which involves high-pressure steam to kill microorganisms. Ethanol (70-90%) is also effective in denaturing proteins and disrupting cell membranes, thereby killing bacteria and viruses. Ultraviolet (UV) light, particularly at 254 nm, can also inactivate DNA and RNA, effectively sterilizing sputum.

**Why Each Wrong Option is Incorrect**
**Option A:** Autoclaving is indeed a method to sterilize sputum, so this option is correct and should be excluded from the distractors.
**Option B:** Ethanol is also a valid method for sterilizing sputum, so this option should be replaced with an incorrect one.
**Option B:** Ethylene oxide is a gas used for sterilizing heat-sensitive materials, but it is not typically used for sputum sterilization due to its toxicity and the need for specialized equipment.
**Option C:** Glutaraldehyde is a potent disinfectant used for sterilizing equipment, but it is not typically used for sputum sterilization due to its toxicity and potential for skin irritation.

**Clinical Pearl / High-Yield Fact**
When handling sputum samples, it's essential to use sterile techniques and equipment to prevent contamination and ensure accurate results. Autoclaving and ethanol are commonly used methods for sterilizing sputum, while UV light can be used for surface disinfection.

**Correct Answer: C. Glutaraldehyde is a potent disinfectant used for sterilizing equipment, but it is not typically used for sputum sterilization due to its toxicity and potential for skin irritation.**