**Core Concept**
The question is referring to the concept of relative risk (RR), which is a measure used in epidemiology to compare the risk of developing a disease among exposed individuals to that among non-exposed individuals.

**Why the Correct Answer is Right**
Relative risk (RR) is calculated as the ratio of the incidence of disease among exposed individuals to the incidence of disease among non-exposed individuals. It provides a quantitative estimate of the association between an exposure and the risk of developing a disease. In formula form, RR = (Incidence rate among exposed) / (Incidence rate among non-exposed). This calculation allows researchers to assess the strength of the association between the exposure and the disease.

**Why Each Wrong Option is Incorrect**
**Option A:** This is incorrect because it does not accurately describe the calculation of relative risk. The relative risk is the ratio of the incidence among exposed to the incidence among non-exposed, not the other way around.
**Option B:** This is incorrect because it describes the odds ratio, which is a different measure used in epidemiology to compare the odds of developing a disease among exposed individuals to that among non-exposed individuals.
**Option C:** This is incorrect because it is a partial description of the relative risk, but it lacks the numerator (incidence among exposed) and is therefore incomplete.

**Clinical Pearl / High-Yield Fact**
A key concept in epidemiology is that the relative risk is always greater than or equal to 1, with 1 indicating no association between the exposure and the disease. A relative risk less than 1 indicates that the exposure is protective, while a relative risk greater than 1 indicates that the exposure is harmful.

**Correct Answer:** D. The incidence of disease among exposed divided that of non-exposed is equal to Relative Risk.