**Core Concept**
The question tests the understanding of epidemiological terms, specifically **incidence** and **prevalence**. Incidence refers to the number of new cases of a disease in a population over a certain period, while prevalence is the total number of cases, including both new and existing ones, at a given time.

**Why the Correct Answer is Right**
To calculate prevalence, we use the formula: Prevalence = Incidence x Duration. Given the incidence is 100 in 1 year and the duration of the disease is 2 years, we can calculate the prevalence as 100 x 2 = 200. This means that out of 5000, 200 people will have the disease at any given time over the 2-year period.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because it does not account for the duration of the disease.
**Option B:** This option is also incorrect as it miscalculates the prevalence by not considering the correct formula.
**Option D:** This option is wrong because it does not apply the correct epidemiological formula for calculating prevalence.

**Clinical Pearl / High-Yield Fact**
Remember, **prevalence** gives an idea of the burden of a disease in a population, while **incidence** helps in understanding the risk of developing the disease. The formula Prevalence = Incidence x Duration is crucial for calculations.

**Correct Answer:** C. 200