**Core Concept**
The question requires knowledge of sputum disinfection, which is a critical step in laboratory procedures to prevent the spread of infectious diseases. Effective disinfection involves the use of chemical agents that can inactivate or destroy pathogenic microorganisms, including bacteria, viruses, and fungi.

**Why the Correct Answer is Right**
The correct answer involves the use of glutaraldehyde, a potent disinfectant that is commonly used to disinfect sputum and other respiratory specimens. Glutaraldehyde works by cross-linking proteins and inactivating enzymes, ultimately leading to the death of microorganisms. It is particularly effective against viruses, including influenza and respiratory syncytial virus (RSV), which are commonly found in sputum samples. Glutaraldehyde is also used to disinfect medical equipment and instruments.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because bleach is a strong disinfectant, but it is not the preferred choice for disinfecting sputum due to its harsh corrosive properties and potential to damage laboratory equipment.
**Option B:** This option is incorrect because formaldehyde is a disinfectant, but it is not commonly used for sputum disinfection due to its toxicity and potential health hazards.
**Option C:** This option is incorrect because iodine is a disinfectant, but it is not typically used for sputum disinfection due to its limited effectiveness against certain types of bacteria and viruses.

**Clinical Pearl / High-Yield Fact**
It is essential to follow proper laboratory protocols and use personal protective equipment (PPE) when handling sputum samples to prevent the spread of infectious diseases.

**Correct Answer: C. Glutaraldehyde**