Which among the following is exclusively marine?

Options

A. Porifera
B. Echinodermata
C. Mollusca
D. Pisces

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks which organism is exclusively found in marine environments. This means we need to identify an organism that does not inhabit freshwater or terrestrial environments.

2. **Reviewing the Options**: The options provided are:
- Porifera
- Echinodermata
- Mollusca
- Pisces

3. **Analyzing Each Option**:
- **Porifera**: This group includes sponges, which can be found in both marine and freshwater environments. Therefore, they are not exclusively marine.
- **Echinodermata**: This group includes organisms like starfish and sea urchins. They are exclusively marine and are only found in marine habitats.
- **Mollusca**: This group includes animals like octopuses and snails, which can inhabit both freshwater and marine environments. Thus, they are not exclusively marine.
- **Pisces**: This group refers to fishes, which can also be found in both freshwater and marine environments. Therefore, they are not exclusively marine.

4. **Identifying the Correct Answer**: Based on the analysis, the only group that is exclusively marine is **Echinodermata**.

5. **Conclusion**: The correct answer to the question is **Echinodermata**.

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