Nereis belongs is

Options

A. Mollusca
B. Arthropoda
C. Echinodermata
D. Annelida

Answer

### Step-by-Step Solution:

1. **Identify the Organism**: The question asks about "Nereis," which is a genus of marine polychaete worms.

2. **Understand the Characteristics of Nereis**: Nereis is known for its segmented body structure. Each segment is equipped with bristles called setae, which aid in locomotion.

3. **Review the Options Given**:
- **Mollusca**: This phylum includes organisms like snails and octopuses, which do not have segmented bodies.
- **Arthropoda**: This phylum includes insects, arachnids, and crustaceans. While they are segmented, Nereis is not classified under this phylum.
- **Echinodermata**: This phylum includes starfish and sea urchins, which are not segmented worms.
- **Annelida**: This phylum includes segmented worms like earthworms and polychaetes (including Nereis).

4. **Eliminate Incorrect Options**: Based on the characteristics of Nereis, we can eliminate Mollusca and Echinodermata because they do not possess the segmented body structure that Nereis has.

5. **Confirm the Correct Classification**: Since Nereis has a segmented body and numerous setae, it clearly belongs to the phylum Annelida.

6. **Final Answer**: Therefore, the correct answer is that Nereis belongs to the phylum **Annelida**.