**Core Concept**
Disinfection of sputum following expectoration is a crucial step in preventing the spread of respiratory pathogens, particularly in healthcare settings. This process involves inactivating or destroying microorganisms on the surface of the sputum, thereby reducing the risk of infection transmission.

**Why the Correct Answer is Right**
The correct term for disinfecting sputum immediately following expectoration is autoclaving. Autoclaving involves exposing the sputum to high-pressure steam, typically at 121°C for 15-20 minutes, to achieve complete sterilization. This process is effective against a wide range of microorganisms, including bacteria, viruses, and fungi. Autoclaving is a reliable method for disinfecting sputum, especially in situations where immediate disposal is not feasible.

**Why Each Wrong Option is Incorrect**
* **Option A:** There is no widely recognized term "sputum sterilization" in medical literature, and it does not accurately describe the process of disinfecting sputum.
* **Option B:** "Immediate disposal" is not a method of disinfection but rather a practice of removing potentially infectious materials from the environment.
* **Option C:** "Sputum disinfectant" is a vague term that could refer to various chemicals or agents used for disinfecting sputum, but it does not specifically describe the process of autoclaving.

**Clinical Pearl / High-Yield Fact**
When handling potentially infectious materials like sputum, it is essential to follow strict protocols for disinfection and disposal to prevent transmission of pathogens to healthcare workers and patients.

**Correct Answer:** A. Autoclaving.