**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 used to estimate the increased risk of a particular outcome in individuals exposed to a specific risk factor, such as mobile phone use while driving.

**Why the Correct Answer is Right**
To calculate Relative Risk, we need to compare the risk of the outcome (accident) in the exposed group (truck drivers using mobile while driving) to the risk in the non-exposed group (truck drivers not using mobile while driving). The formula for Relative Risk is: RR = (Risk in exposed group) / (Risk in non-exposed group). In this case, the risk in the exposed group is 300/1000 = 0.3, and the risk in the non-exposed group is 300/5000 = 0.06. Therefore, RR = 0.3 / 0.06 = 5.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it is a placeholder and does not provide a valid answer.
**Option B:** This option is incorrect because it does not provide a valid calculation for Relative Risk.
**Option C:** This option is incorrect because it is not the correct formula for Relative Risk.

**Clinical Pearl / High-Yield Fact**
When calculating Relative Risk, it's essential to consider the baseline risk in the non-exposed group, as it serves as the denominator for the calculation. In this case, the baseline risk of accidents in non-mobile-using truck drivers is 6%.

**Correct Answer:** C.