**Core Concept**
Lugol's Iodine is a solution used in various medical applications, including disinfection and diagnostic purposes. It is composed of a combination of elemental iodine and potassium iodide, which provides its unique properties.

**Why the Correct Answer is Right**
The correct answer contains a combination of 5% elemental iodine and 10% potassium iodide in a water solution. This specific ratio of iodine and potassium iodide is crucial for Lugol's Iodine's effectiveness. The iodine in Lugol's Iodine acts as a disinfectant and antiseptic, while the potassium iodide enhances its solubility and stability. When Lugol's Iodine is applied to the skin or mucous membranes, the iodine is released, allowing it to interact with and inactivate pathogens.

**Why Each Wrong Option is Incorrect**
**Option A:** 5% Iodine in ethanol - While iodine in ethanol is used as a disinfectant, the addition of potassium iodide is what makes Lugol's Iodine unique, so this option is incorrect.
**Option B:** 10% Iodine in water - This option lacks potassium iodide, which is essential for Lugol's Iodine's properties and effectiveness.
**Option C:** 5% Iodine in glycerin - Glycerin is not a component of Lugol's Iodine, making this option incorrect.

**Clinical Pearl / High-Yield Fact**
Lugol's Iodine is often used in ophthalmology to diagnose and treat conditions such as conjunctivitis and keratitis. It is also used as a skin disinfectant before surgical procedures.

**Correct Answer: C. 5% elemental iodine and 10% potassium iodide in a water solution.**