**Core Concept**
Fluoride levels in drinking water are crucial for preventing dental caries while minimizing the risk of dental fluorosis. The optimal fluoride concentration is essential to achieve this balance, which is influenced by factors like age, climate, and geographic location.

**Why the Correct Answer is Right**
The recommended fluoride levels in drinking water are typically set between 0.7 and 1.2 milligrams per liter (mg/L). This range is based on the concept of "optimal fluoride" which aims to reduce dental caries by approximately 50% to 60% while minimizing the risk of dental fluorosis. The optimal fluoride levels are determined by the Community Water Fluoridation (CWF) program, which considers various factors including the age and socio-economic status of the population.

**Why Each Wrong Option is Incorrect**
**Option A:** 0.5 mg/L is too low to effectively prevent dental caries, and communities with this level may experience increased rates of tooth decay.
**Option B:** 1.5 mg/L is higher than the recommended level and may lead to an increased risk of dental fluorosis, especially in children.
**Option C:** 2.0 mg/L is excessively high and can cause severe dental fluorosis, including pitting and discoloration of teeth.

**Clinical Pearl / High-Yield Fact**
A commonly used mnemonic to remember the optimal fluoride levels is "0.7 to 1.2, a perfect pair!" This helps students recall the recommended range.

**Correct Answer: C. 1.2 mg/L**