**Core Concept**
Defluoridation of water refers to the process of removing excess fluoride from drinking water, which is essential to prevent fluorosis, a condition characterized by the deposition of fluoride ions in the bones and teeth, leading to skeletal and dental abnormalities.

**Why the Correct Answer is Right**
The correct answer is related to the use of activated alumina (Al2O3) for defluoridation. Activated alumina is a type of adsorbent that has a high affinity for fluoride ions, allowing it to effectively remove them from water. The process involves passing the water through a bed of activated alumina, which traps the fluoride ions, resulting in deionized water.

**Why Each Wrong Option is Incorrect**
**Option A:** Ion exchange resins are used for removing other ions such as sodium, potassium, and calcium but not specifically fluoride.
**Option B:** Reverse osmosis can remove various contaminants, including fluoride, but it is not the most efficient method for defluoridation.
**Option C:** Distillation can also remove fluoride from water, but it is a more energy-intensive process compared to using activated alumina.

**Clinical Pearl / High-Yield Fact**
Activated alumina is a widely used and cost-effective method for defluoridation, and its effectiveness is due to the high surface area and adsorption capacity of the material.

**Correct Answer:** C. Activated alumina