**Core Concept**
The gingival index is a widely used clinical measure to assess the severity of gingivitis, a common periodontal disease characterized by inflammation of the gingiva (gums). The gingival index takes into account the color, texture, and bleeding of the gingiva in order to evaluate its health status.

**Why the Correct Answer is Right**
The gingival index is a subjective measure, relying on the clinical judgment of the examiner to assess the gingival health. It is scored on a scale from 0 to 3, where 0 indicates healthy gingiva, and 3 indicates severe inflammation. The gingival index is a useful tool for monitoring the effectiveness of oral hygiene practices and periodontal treatments. However, it has limitations, including inter-examiner variability and the subjective nature of the assessment.

**Why Each Wrong Option is Incorrect**
**Option A:** The gingival index is a widely accepted and standardized measure for assessing gingivitis. It is not false to say that the gingival index is a commonly used measure.

**Option B:** The gingival index is indeed a subjective measure, relying on the clinical judgment of the examiner. Therefore, stating that it is a subjective measure is not false.

**Option C:** The gingival index is not a quantitative measure. It is a categorical scale used to assess the severity of gingivitis. Therefore, stating that it is a quantitative measure is false.

**Clinical Pearl / High-Yield Fact**
A key aspect to remember when using the gingival index is that it is a subjective measure and can be influenced by the examiner's experience and bias. To minimize this variability, it is essential to use standardized criteria and to have multiple examiners assess the gingiva to increase reliability.

**Correct Answer: C. The gingival index is a quantitative measure.**