**Core Concept:**
The question is about calculating the case fatality rate (CFR) in an outbreak scenario. CFR is a measure of mortality in an infectious disease outbreak and is calculated as the number of deaths divided by the number of cases, multiplied by 100.

**Why the Correct Answer is Right:**
In this question, we are given the number of cases (20) and deaths (5). The case fatality rate can be calculated as:

(Number of deaths / Number of cases) x 100
= (5 / 20) x 100
= 25%

**Why Each Wrong Option is Incorrect:**
A. This option is incorrect because the calculation does not match the actual CFR found in the question (25%).
B. This option is incorrect because the calculation does not match the actual CFR found in the question (25%).
C. This option is incorrect because the calculation does not match the actual CFR found in the question (25%).
D. This option is incorrect because the calculation does not match the actual CFR found in the question (25%).

**Why the Correct Answer is Right:**
The correct answer, **25%, accurately represents the mortality rate in this outbreak scenario, which is calculated as the ratio of deaths to cases (5/20) multiplied by 100. The high CFR indicates a serious public health issue and emphasizes the need for proper control measures and treatment strategies to reduce the number of deaths and control the outbreak.

**Why Each Wrong Option is Incorrect:**
A. The incorrect answer is not relevant to the given data and does not represent the mortality rate accurately.
B. The incorrect answer is not relevant to the given data and does not represent the mortality rate accurately.
C. The incorrect answer is not relevant to the given data and does not represent the mortality rate accurately.
D. The incorrect answer is not relevant to the given data and does not represent the mortality rate accurately.

**Clinical Pearls:**
A high CFR in an outbreak indicates a serious public health issue. It highlights the need to identify the causative organism, implement appropriate treatment and control measures, and provide necessary preventive strategies to reduce the mortality rate and control the outbreak. A careful assessment of risk factors, case fatality, and transmission should be performed to design an effective control strategy.