## Core Concept
The question pertains to **craniometry** and **anthropology**, specifically focusing on the classification of human races based on skull morphology. The features mentioned, such as the shape of the nasal opening, the form of the palate, the shape of the orbits, and the cephalic index, are used to differentiate between various racial groups.

## Why the Correct Answer is Right
The description provided - **rounded nasal opening**, **horseshoe-shaped palate**, **round orbits**, and a **cephalic index above 80** - aligns with the characteristics of the **Negroid** or **African** race.
- A **rounded nasal opening** and **round orbits** are typical of Negroid skulls.
- A **horseshoe-shaped palate** is also a characteristic feature.
- The **cephalic index** (the ratio of the width of the head multiplied by 100 divided by its length) being **above 80** indicates a **brachycephalic** (short-headed) skull, which can be found in various races but in combination with other features mentioned, supports the classification.

## Why Each Wrong Option is Incorrect
- **Option A:** Without specific details on the characteristics of race A, we cannot directly refute, but given that the description fits Negroid/African features, if A does not match, it's incorrect.
- **Option B:** Similarly, without specifics, if B doesn't align with the Negroid features, it's incorrect.
- **Option C:** If C suggests another racial category not aligning with the provided skull features, it's incorrect.

## Clinical Pearl / High-Yield Fact
A key point to remember is that **racial classification based on skull morphology** is an outdated practice and not commonly used in modern anthropology or clinical practice due to its limitations and the significant variability within populations. However, for the purpose of certain exams or historical contexts, being familiar with these classic descriptions is necessary.

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