Which echinoderm is fresh water ?

Options

A. Asterias
B. Pentaceros
C. Astropecten
D. None of the above.

Answer

### Step-by-Step Solution:

1. **Understanding Echinoderms**: Echinoderms are marine animals that belong to the phylum Echinodermata. They are characterized by their radial symmetry, triploblastic organization, and organ-level organization.

2. **Identifying Freshwater Echinoderms**: The question specifically asks for freshwater echinoderms. It is important to note that echinoderms are exclusively marine and do not inhabit freshwater environments.

3. **Analyzing the Options**:
- **Asterius**: This is a genus of starfish, which are marine organisms. Therefore, this option is incorrect.
- **Pentaceros**: This is not an echinoderm; it is a ray-finned fish belonging to the phylum Chordata. Hence, this option is also incorrect.
- **Astropectin**: This is another genus of starfish, which again are marine organisms. Thus, this option is incorrect as well.
- **None of the Above**: Since all the previous options are incorrect, this option is the correct answer.

4. **Conclusion**: There are no freshwater echinoderms. All the options provided are either marine echinoderms or not echinoderms at all. Therefore, the answer to the question is "None of the Above".