## Core Concept
The Ponderal index, also known as Rohrer's index, is a measure used to assess leanness or corpulence of a person calculated as a relationship of mass to height. It is defined as the ratio of body mass (in kilograms) to the cube of the height (in meters), i.e., (Ponderal index = frac{Mass (kg)}{Height^3 (m^3)}). This index is often used in pediatric populations to evaluate growth and nutritional status.

## Why the Correct Answer is Right
The correct statement regarding the Ponderal index involves understanding its formula and application. The Ponderal index is specifically calculated using the formula ( frac{kg}{m^3} ), which directly relates body mass to the cube of height. This calculation helps in assessing whether a child is underweight, normal, or overweight based on their mass and height.

## Why Each Wrong Option is Incorrect
- **Option A:** Without the specific details of option A, we cannot directly assess its accuracy. However, any statement contradicting the basic definition or calculation of the Ponderal index would be incorrect.
- **Option B:** Similarly, without specifics, we assume any statement not aligning with established facts about the Ponderal index, such as its use or calculation, would be wrong.
- **Option C:** This option's accuracy depends on its content. If it misrepresents the Ponderal index's definition, application, or units, it would be incorrect.
- **Option D:** Given as the correct answer, any statement here that aligns with incorrect representations of the Ponderal index would indeed be not true.

## Clinical Pearl / High-Yield Fact
A key point to remember is that the Ponderal index is an important tool in pediatrics for evaluating growth patterns. A normal Ponderal index ranges approximately from 11 to 13. A value less than 11 may indicate wasting, while a value greater than 13 may suggest obesity. This index is particularly useful because it does not require age as a variable, making it helpful in assessing growth in preterm infants or in cases where age is uncertain.

## Correct Answer: D.