## Core Concept
The definition of public health is rooted in the concept of preventing disease and promoting health at the population level. Public health is concerned with protecting and improving the health of communities through education, policy-making, and research. The definition aims to capture the essence of this field.

## Why the Correct Answer is Right
The definition of public health was given by **WHO** (World Health Organization) in 1946, which states: "Public health is the science and art of preventing disease, prolonging life and promoting health through the organized efforts of society." This definition emphasizes the organized efforts of society to prevent disease, prolong life, and promote health.

## Why Each Wrong Option is Incorrect
* **Option A:** Not provided, hence cannot be evaluated.
* **Option B:** Not provided, hence cannot be evaluated.
* **Option D:** Not provided, hence cannot be evaluated.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the **WHO** definition of public health highlights the importance of organized societal efforts in achieving health goals. This definition is significant as it sets the stage for public health policy and practice globally.

## Correct Answer Line
**Correct Answer: C. WHO.**