**Core Concept**
Glutaraldehyde is a high-level disinfectant commonly used for sterilizing medical equipment such as endoscopes, which cannot withstand high temperatures or harsh chemicals. Its effectiveness lies in its ability to denature proteins and disrupt cell membranes.

**Why the Correct Answer is Right**
Glutaraldehyde works by covalently binding to amino groups in proteins, ultimately leading to the denaturation and inactivation of enzymes. This process prevents the growth of microorganisms, including bacteria, viruses, and fungi. The use of glutaraldehyde for endoscope sterilization is recommended by various guidelines due to its broad-spectrum activity and stability at room temperature. The recommended concentration of glutaraldehyde for this purpose is typically 2%.

**Why Each Wrong Option is Incorrect**
**Option B:** Formalin is a fixative and a disinfectant, but it is not suitable for sterilizing endoscopes due to its toxicity and potential to damage equipment.
**Option C:** Autoclaving is a reliable method for sterilizing heat-resistant equipment, but it would damage the fragile endoscope tube. High temperatures and pressure would also compromise the integrity of the equipment.
**Option D:** Boiling water is not sufficient to sterilize endoscopes, as it may not reach the necessary temperatures to kill all microorganisms, particularly spores.

**Clinical Pearl / High-Yield Fact**
When handling glutaraldehyde, it is essential to wear protective gloves and work in a well-ventilated area due to its respiratory and skin irritant properties.

**✓ Correct Answer: A. Glutaraldehyde**