**Core Concept**
Body mass index (BMI) is a widely used measurement to categorize individuals as underweight, normal weight, overweight, or obese based on their weight and height. Other indices, such as Quetlet's index, Corpulence index, and BMI itself, are used to define obesity. However, Chandler's index is not a commonly recognized or used measure for obesity.

**Why the Correct Answer is Right**
Chandler's index is not a valid or recognized measure for obesity. In contrast, Quetlet's index, also known as the Quetlet index or the body mass index (BMI), is a widely accepted and used measure for obesity. It is calculated as weight in kilograms divided by the square of height in meters. The Corpulence index is another measure that is used to define obesity. It is calculated as the ratio of weight to height, but it is not as commonly used as BMI. Chandler's index, on the other hand, is not a recognized or used measure for obesity, making it an outlier among the options.

**Why Each Wrong Option is Incorrect**
**Option B:** Corpulence index is a valid measure for obesity, although it is not as commonly used as BMI.
**Option C:** Quetlet's index, or BMI, is a widely accepted and used measure for obesity.
**Option D:** Body mass index is indeed a valid measure for obesity.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize that BMI is a widely used and accepted measure for obesity, and it is essential to use it correctly to define obesity in clinical and public health settings. BMI has its limitations, but it remains a valuable tool for assessing weight status.

**✓ Correct Answer: A. Chandler's index**