**Core Concept**
Prevalence and incidence are two important epidemiological measures used to describe the distribution and burden of diseases within a population. Prevalence refers to the total number of cases of a disease present in a population at a specific point in time, whereas incidence represents the number of new cases that occur within a population over a specified period.

**Why the Correct Answer is Right**
Incidence is indeed a rate, as it measures the frequency of new events (in this case, disease occurrences) per unit of time (e.g., per 1000 people per year). This rate is calculated by dividing the number of new cases by the population at risk over a specified period. In contrast, prevalence is a proportion, not a rate, as it represents the total number of cases (both new and existing) present in the population at a given time. Prevalence is calculated by dividing the total number of cases by the population size.

**Why Each Wrong Option is Incorrect**
**Option A:** Both incidence and prevalence are not rates; prevalence is a proportion, and incidence is a rate. This statement is incorrect because it misclassifies prevalence.
**Option B:** Prevalence is not a rate, but incidence is. This statement is incorrect because it misclassifies prevalence, which is a proportion, not a rate.
**Option D:** Both prevalence and incidence are not rates; prevalence is a proportion, and incidence is a rate. This statement is incorrect because it inaccurately describes incidence as not a rate.

**Clinical Pearl / High-Yield Fact**
It's essential to remember the distinction between incidence and prevalence, as they provide different insights into the epidemiology of a disease. Incidence is useful for understanding the risk of developing a disease, while prevalence provides information on the overall burden of a disease within a population.

✓ Correct Answer: C. Incidence is a rate but prevalence is not.