## Core Concept
The question tests knowledge of various sterilizing and disinfecting agents used in medical settings. Sterilization and disinfection are critical in eliminating or reducing microbial loads on surfaces, equipment, and in some cases, tissues. Different agents have different mechanisms of action and effectiveness against various types of microbes.

## Why the Correct Answer is Right
Ethanol (70%) is a commonly used disinfectant effective against many bacteria, viruses, and fungi. Isopropyl alcohol, also known as rubbing alcohol, is another widely used disinfectant. Glutaraldehyde is a high-level disinfectant used for cleaning heat-sensitive equipment. Chlorhexidine is an antiseptic rather than a disinfectant or sterilizing agent; it's primarily used on living tissues to reduce microbial load, especially in skin preparation before injections or surgeries.

## Why Each Wrong Option is Incorrect
* **Option A:** Ethanol (70%) - This is a known disinfectant.
* **Option B:** Isopropyl alcohol - Also a known disinfectant.
* **Option D:** Glutaraldehyde - Used as a high-level disinfectant.

## Clinical Pearl / High-Yield Fact
A key point to remember is the difference between antiseptics and disinfectants. Antiseptics are used on living tissues and are less toxic, while disinfectants are used on non-living surfaces. Chlorhexidine, mentioned in the correct answer, is an example of an antiseptic.

## Correct Answer: . Chlorhexidine