The third name in trinomial nomenclature is

Options

A. species
B. subgenus
C. subspecies
D. ecotype.

Explanation

### Step-by-Step Solution:

1. **Understanding Nomenclature**: Nomenclature is a system of naming organisms. The most common system used in biology is binomial nomenclature, which consists of two parts: the genus name and the species name.

2. **Binomial Nomenclature**: In binomial nomenclature, the first name represents the genus (e.g., "Naja" for cobra), and the second name represents the species (e.g., "Naja" again for the specific species of cobra).

3. **Introduction to Trinomial Nomenclature**: Trinomial nomenclature expands on binomial nomenclature by adding a third name. This system is used when it is necessary to identify subspecies within a species.

4. **Components of Trinomial Nomenclature**: In trinomial nomenclature, the three parts are:
- The first part is the genus name.
- The second part is the species name.
- The third part is the subspecies name, which indicates a specific variant of the species that exists in a particular geographical area.

5. **Example of Trinomial Nomenclature**: For instance, if we take the example of crows, the species might be identified as "Corvus corax" (the common raven), and if we have a subspecies found in a specific region, it could be "Corvus corax corax". Here, "corax" is the subspecies name.

6. **Conclusion**: Therefore, the third name in trinomial nomenclature is referred to as the **subspecies**.