**Core Concept**
The fluoride index is a measure used to assess the risk of dental fluorosis in children. It is calculated based on the concentration of fluoride in the drinking water. At 8 ppm (parts per million), the risk of dental fluorosis increases, making it essential to monitor and manage fluoride levels.

**Why the Correct Answer is Right**
The best fluoride index at 8 ppm water level is the Translucency Enamel Index (TFE). TFE is a widely used index that assesses the severity of dental fluorosis by evaluating the translucency of the enamel. It ranges from 0 (no change) to 5 (maximum change), with higher scores indicating more severe fluorosis. At 8 ppm, the risk of moderate to severe fluorosis increases, making TFE a suitable index for assessing the severity of fluorosis.

**Why Each Wrong Option is Incorrect**
**Option A:** The Community Fluorosis Index (CFI) is not the best index at 8 ppm water level because it is more of a general indicator of community water fluorosis rather than a specific measure of the severity of fluorosis.
**Option B:** The Tsunami Index is not a recognized measure of dental fluorosis and is not relevant to assessing the severity of fluorosis at 8 ppm water level.
**Option C:** The Fluorosis Index (FI) is a general term and not a specific, widely accepted measure of dental fluorosis severity.

**Clinical Pearl / High-Yield Fact**
When assessing dental fluorosis, it's essential to consider the concentration of fluoride in the drinking water, as well as the duration of exposure. The American Dental Association recommends a fluoride level of 0.7 ppm to prevent dental caries while minimizing the risk of fluorosis.

**Correct Answer: B. Translucency Enamel Index (TFE)**