**Core Concept**
The question is testing knowledge of antiseptics and disinfectants, specifically their sporicidal activity. Sporicidal agents are capable of killing bacterial spores, which are highly resistant to environmental stress and can survive extreme conditions.

**Why the Correct Answer is Right**
Glutaraldehyde is a potent sporicidal agent due to its ability to cross-link proteins and inactivate enzymes essential for spore germination and outgrowth. Its broad-spectrum activity against bacteria, viruses, and fungi, including spores, makes it a valuable disinfectant in healthcare settings. Glutaraldehyde's efficacy against spores is attributed to its ability to penetrate the spore coat and inactivate the core enzymes.

**Why Each Wrong Option is Incorrect**
**Option A:** Ethanol is not sporicidal; it is primarily bactericidal and virucidal but does not have significant activity against bacterial spores.
**Option B:** Hydrogen peroxide is not sporicidal; it is a weak oxidizing agent that is effective against bacteria and viruses but does not have sufficient activity against spores.
**Option C:** Chlorhexidine is not sporicidal; it is a broad-spectrum antimicrobial agent effective against bacteria, viruses, and fungi but does not have significant activity against spores.

**Clinical Pearl / High-Yield Fact**
When choosing a disinfectant for sporicidal activity, consider the specific use and location (e.g., operating room versus patient care area). Always follow the manufacturer's instructions for dilution and contact time to ensure efficacy.

**Correct Answer: A. Ethanol.**