**Core Concept**
The cephalic index is a quantitative measure used to classify the shape and size of the human skull. It is calculated by dividing the maximum width of the cranial cavity by its maximum length, then multiplying the result by 100.

**Why the Correct Answer is Right**
The cephalic index is a crucial anthropometric parameter that helps in determining the racial or ethnic origin of a person. It is particularly useful in forensic anthropology and in the study of human evolution. The cephalic index ranges from 0 to 200, and different values are associated with different racial groups, such as dolichocephalic (long-headed), brachycephalic (short-headed), and mesocephalic (medium-headed) skulls.

**Why Each Wrong Option is Incorrect**
**Option A:** The cephalic index is not a measure of facial structure.
**Option B:** The cephalic index is not a measure of overall body size or proportion.
**Option C:** The cephalic index is not a measure of cranial capacity or intelligence.

**Clinical Pearl / High-Yield Fact**
The cephalic index can be a useful tool in forensic anthropology, particularly in the identification of human remains. It can also provide valuable information about the evolutionary history of a particular population.

**Correct Answer: B. Determination of racial or ethnic origin.**