## Core Concept
The case fatality rate (CFR) is a measure used in epidemiology to describe the severity of a disease. It is defined as the proportion of deaths within a designated population of people with a particular condition over the course of the disease. The CFR is often expressed as a percentage and is a critical indicator of the lethality of a disease.

## Why the Correct Answer is Right
The correct formula for the case fatality rate is: **(Number of deaths due to the disease / Number of confirmed cases of the disease) × 100**. This measure provides insight into the severity and outcome of a disease, helping in assessing the risk and planning for healthcare resources. It is particularly useful in comparing the lethality of different diseases or outbreaks.

## Why Each Wrong Option is Incorrect
- **Option A:** This option is incorrect because it does not accurately represent the formula for the case fatality rate. Without the specific details of what A represents, it's clear that it does not match the standard definition.
- **Option B:** Similarly, this option does not correctly define the case fatality rate. The actual formula involves the number of deaths due to the disease divided by the number of cases, not necessarily reflecting what B proposes.
- **Option C:** This option might seem plausible but does not accurately represent the case fatality rate. The correct calculation involves a direct ratio of deaths to cases, not a comparison over a period in the way C suggests.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the case fatality rate can vary significantly between diseases. For example, the CFR for Ebola can be as high as 90%, while for many seasonal influenzas, it is less than 1%. Understanding the CFR helps in public health planning and in communicating the risk of a disease to the public.

## Correct Answer: D. (Number of deaths due to the disease / Number of confirmed cases of the disease) × 100.