**Core Concept**
Sporicidal disinfectants are essential for controlling infections caused by bacterial spores. These disinfectants work by disrupting the spore's outer coat, ultimately leading to the death of the enclosed bacterial cell.

**Why the Correct Answer is Right**
Glutaraldehyde is a broad-spectrum disinfectant that is effective against a wide range of microorganisms, including bacteria, viruses, and fungi. However, it is not effective against bacterial spores, which have a highly resistant outer coat. Glutaraldehyde can penetrate the spore coat and inactivate the spore, but it may not be able to kill all spores, especially those with a high level of resistance.

**Why Each Wrong Option is Incorrect**
**Option A:** Formaldehyde is a sporicidal disinfectant that is effective against bacterial spores. It works by coagulating proteins and disrupting the spore's outer coat.
**Option B:** Hydrogen peroxide is also a sporicidal disinfectant that can kill bacterial spores. It works by releasing oxygen radicals that damage the spore's DNA and proteins.
**Option C:** Ethylene oxide is a sporicidal gas that is effective against bacterial spores. It works by alkylating the spore's DNA and proteins, ultimately leading to the death of the enclosed bacterial cell.

**Clinical Pearl / High-Yield Fact**
When using disinfectants, it's essential to choose the right one for the job. For example, for disinfecting surfaces that may come into contact with spores, use a sporicidal disinfectant like formaldehyde or hydrogen peroxide.

**Correct Answer: C. Ethylene oxide is a sporicidal gas that is effective against bacterial spores.**