## Core Concept
Puppe's rule, also known as Puppe's index or cephalic index, is related to **forensic anthropology** and **criminology**. It is used to classify the skulls into different categories based on their shape and size. This classification can sometimes be associated with racial or ethnic groups.

## Why the Correct Answer is Right
Puppe's rule is specifically related to the classification of skulls, particularly in the context of **racial anthropology** or **forensic science**. I.C. Puppe, a criminologist, developed a system to categorize skulls based on their **cephalic index**, which is calculated by measuring the ratio of the maximum width of the skull to its maximum length, then multiplying by 100. This index helps in differentiating between various **racial or ethnic groups** based on cranial morphology.

## Why Each Wrong Option is Incorrect
- **Option A:** Without specific details on what option A entails, it's hard to directly refute it. However, if it does not relate to the classification of skulls or cephalic index, then it would be incorrect.
- **Option B:** Similarly, without specifics, if option B does not pertain to forensic anthropology, criminology, or a method of skull classification, it would be incorrect.
- **Option C:** If option C suggests a different application or context not related to Puppe's rule or cephalic index, it would be incorrect.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **Puppe's rule** or the **cephalic index** has been used historically in **anthropology** and **forensic science** for classification purposes. However, its use and implications have been subjects of ethical and scientific debate, especially concerning **racial classification**.

## Correct Answer Line
**Correct Answer: D.**