**Core Concept**
Point Prevalence is a measure used in epidemiology to estimate the total number of existing cases of a disease or condition within a population at a specific point in time. It is a snapshot of the disease burden at a particular moment, providing valuable information for public health planning and resource allocation.

**Why the Correct Answer is Right**
The correct definition of Point Prevalence is **D. Number of total cases at a given point of time**. This is because Point Prevalence aims to capture the cumulative number of existing cases, including both new and old cases, within a population at a specific point in time. It does not account for the incidence of new cases over a period, making **Option A** incorrect. Similarly, Point Prevalence is not concerned with the total number of cases over a year, making **Option C** incorrect. **Option B** is also incorrect as it refers to the incidence of new cases in a given year, which is a different measure.

**Why Each Wrong Option is Incorrect**
**Option A:** This option refers to the incidence of new cases at a given point in time, which is not the same as Point Prevalence. Incidence measures the number of new cases occurring within a specified period.
**Option B:** This option is incorrect as it refers to the cumulative incidence of new cases in a given year, which is a measure of the number of new cases occurring within a specified period, not the total number of existing cases at a point in time.
**Option C:** This option is incorrect as it refers to the total number of cases in a given year, which is a measure of the cumulative incidence over a period, not the total number of existing cases at a point in time.

**Clinical Pearl / High-Yield Fact**
To remember the difference between Point Prevalence and Incidence, think of Point Prevalence as a snapshot of the disease burden at a particular moment, while Incidence is like a video recording of new cases occurring over time.

**✓ Correct Answer: D. Number of total cases at a given point of time**