In a village of 1 lakh populations, among 20,000 exposed to smoking, 200 developed cancer, and among 40,000 people enexposed, 40 developed cancer. The relative risk of smoking in the development of cancer is –

**Core Concept**
The 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 used to quantify the association between an exposure and an outcome in epidemiological studies.

**Why the Correct Answer is Right**
To calculate the relative risk, we need to first find the risk of developing cancer among the exposed and non-exposed groups. The risk is calculated as the number of cases divided by the total number of people in each group. The relative risk is then calculated by dividing the risk of cancer among the exposed group by the risk of cancer among the non-exposed group.

Risk in exposed group = (Number of cases in exposed group / Total number of people in exposed group)
= (200 / 20,000)
= 0.01

Risk in non-exposed group = (Number of cases in non-exposed group / Total number of people in non-exposed group)
= (40 / 40,000)
= 0.001

Relative risk = Risk in exposed group / Risk in non-exposed group
= 0.01 / 0.001
= 10

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided.
**Option B:** This option is not provided.
**Option C:** This option is not provided.
**Option D:** This option is not provided.

**Clinical Pearl / High-Yield Fact**
Relative risk is a useful measure of association between an exposure and an outcome, but it does not take into account the baseline risk of the outcome in the population. Therefore, it should be interpreted in the context of the population's baseline risk.

**Correct Answer:**
Correct Answer: D. 10