**Core Concept**
Measure of risk calculated from case-control study is a statistical concept used in epidemiology to quantify the association between a potential risk factor and a disease. It is essential to understand the principles of case-control studies and their limitations when estimating risk.

**Why the Correct Answer is Right**
In a case-control study, the odds ratio (OR) is a widely used measure of risk that estimates the strength of association between the exposure and the disease. The OR is calculated by comparing the odds of exposure among cases (individuals with the disease) to the odds of exposure among controls (individuals without the disease). The OR is a ratio of the odds of exposure in cases to the odds of exposure in controls. It provides an estimate of the relative risk, which is essential in determining the strength of association between the risk factor and the disease.

**Why Each Wrong Option is Incorrect**
**Option A:** **Relative Risk (RR)** - RR is a measure of risk that is typically calculated in cohort studies, not case-control studies.
**Option B:** **Attributable Risk (AR)** - AR is a measure of risk that estimates the proportion of disease incidence that can be attributed to a specific risk factor, but it is not typically calculated in case-control studies.
**Option C:** **Risk Ratio (RR)** - Risk Ratio is another term for Relative Risk, and it is not the correct answer for case-control studies.

**Clinical Pearl / High-Yield Fact**
When interpreting the results of a case-control study, it is essential to remember that the OR is not a direct measure of the absolute risk of developing the disease. Instead, it estimates the relative risk, which can be affected by various biases, such as selection bias and recall bias.

**Correct Answer: C. Odds Ratio**