The members of which of the following phyla are exclusively marine ?

Options

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

Answer

To determine which phylum consists of exclusively marine members, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Analyze Phylum Arthropoda**:
- Arthropoda includes a vast range of organisms such as insects, arachnids, and crustaceans.
- These organisms inhabit various environments, including terrestrial (land) and aquatic (water) ecosystems.
- **Conclusion**: Arthropoda is not exclusively marine.

2. **Analyze Phylum Echinodermata**:
- Echinodermata includes organisms such as starfish, sea urchins, and sea cucumbers.
- All members of this phylum are found exclusively in marine environments.
- **Conclusion**: Echinodermata is exclusively marine.

3. **Analyze Phylum Annelida**:
- Annelida includes segmented worms, such as earthworms and leeches.
- Members of this phylum can be found in both terrestrial and aquatic environments.
- **Conclusion**: Annelida is not exclusively marine.

4. **Analyze Phylum Mollusca**:
- Mollusca includes a diverse group such as snails, clams, and octopuses.
- Members of this phylum can inhabit terrestrial, freshwater, and marine environments.
- **Conclusion**: Mollusca is not exclusively marine.

### Final Answer:
Based on the analysis, the phylum that consists exclusively of marine members is **Echinodermata** (Option B).