**Core Concept**
Relative Risk (RR) is a measure of the ratio of the probability of an event occurring in the exposed group versus the non-exposed group. It is a valuable tool in epidemiological studies to assess the strength of association between a risk factor and a disease.

**Why the Correct Answer is Right**
A Cohort study is a type of observational study where two groups are followed over time: one exposed to the risk factor and one not exposed. The exposure is usually the independent variable, and the outcome is the dependent variable. By comparing the incidence of the outcome between the two groups, the Relative Risk can be calculated. This is because Cohort studies measure the incidence of disease in both exposed and unexposed populations, allowing for the calculation of Relative Risk.

**Why Each Wrong Option is Incorrect**
**Option A:** A case study involves in-depth analysis of a single individual or a small group of individuals, which is not suitable for calculating Relative Risk as it requires comparison between two groups.

**Option C:** Case control studies involve selecting individuals with the disease (cases) and those without the disease (controls) and then looking back in time to determine exposure to the risk factor. This type of study is more suited for calculating Odds Ratio, not Relative Risk.

**Option D:** Experimental studies involve manipulating the independent variable to observe the effect on the dependent variable. While these studies can be used to calculate Relative Risk, they are not the primary type of study used to obtain this measure.

**Clinical Pearl / High-Yield Fact**
When interpreting Relative Risk, remember that a value greater than 1 indicates an increased risk of the disease in the exposed group, while a value less than 1 indicates a decreased risk. A Relative Risk of 1 indicates no association between the exposure and the disease.

**✓ Correct Answer: B. Coho study**