**Core Concept**
The cephalic index is a numerical value used in anthropology and forensic medicine to describe the shape and size of the human skull. It is calculated by dividing the maximum width of the head by its maximum length and multiplying by 100. This measurement is used to distinguish between different ethnic groups and to aid in forensic identification.

**Why the Correct Answer is Right**
The cephalic index of 75-80 is characteristic of the Indian population. This range indicates a mesocephalic skull shape, which is a combination of a broad and a long skull. The Indian skull is generally more brachycephalic (short and broad) than dolichocephalic (long and narrow) or mesocephalic skulls found in other populations. The Indian population's cephalic index is influenced by the country's geographical location and the genetic makeup of its inhabitants.

**Why Each Wrong Option is Incorrect**
**Option B:** Europeans typically have a dolichocephalic skull shape, with a cephalic index ranging from 75-80, but this is not as common as in the Indian population. Their skulls are generally longer and narrower.
**Option C:** The Chinese population has a mix of brachycephalic and dolichocephalic skull shapes, but their cephalic index is not typically within the 75-80 range.
**Option D:** Mongolians have a more brachycephalic skull shape, with a cephalic index often above 80, which is not within the given range.

**Clinical Pearl / High-Yield Fact**
Remember that the cephalic index can be used in conjunction with other forensic anthropological techniques, such as examining the nasal index and the shape of the eye orbits, to aid in identifying human remains.

**✓ Correct Answer: A. Indians**