## **Core Concept**
The cephalic index, also known as the cranial index, is a numerical value used in physical anthropology to categorize the skull shapes of different human populations. It is calculated by multiplying the maximum width of the head by 100 and dividing it by its maximum length. This index helps classify human skulls into dolichocephalic (long-headed), mesocephalic (medium-headed), and brachycephalic (short-headed) categories.

## **Why the Correct Answer is Right**
The cephalic index for Negros, or individuals of African descent, typically falls within a certain range that characterizes their cranial morphology. A cephalic index of **75 or less** is generally considered dolichocephalic. Populations of African descent often have a dolichocephalic skull shape.

## **Why Each Wrong Option is Incorrect**
- **Option A:** Without a specific value, it's hard to directly refute, but if it's not indicative of a dolichocephalic index, it would be incorrect in the context of characterizing African populations.
- **Option B:** Similarly, without a specific value or context indicating it's not a dolichocephalic index, we can't directly assess its incorrectness.
- **Option C:** This option is noted as the correct answer but without the actual value provided in the question, we infer based on typical classifications.
- **Option D:** If this option suggests a mesocephalic or brachycephalic index (ranges approximately being 75-80 for mesocephalic and above 80 for brachycephalic), it would be incorrect for characterizing the typical cephalic index of Negros.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that the cephalic index is just one of many physical anthropology metrics and has been used historically to classify human populations. However, its utility and implications in modern anthropology and medicine are subjects of debate, particularly concerning the biological and genetic diversity within and among human populations.

## **Correct Answer:** . 74.