Which one is exclusively marine?

Options

A. Echinodermata
B. Hemichordata
C. Protochordates
D. All

Answer

To determine which option is exclusively marine, we will analyze each of the provided options step by step.

### Step 1: Analyze Echinodermata
- Echinodermata is a phylum that includes organisms such as starfish and sea urchins.
- They are primarily found in marine environments, but some species can also be found in brackish waters.
- **Conclusion**: Echinodermata is mostly marine but not exclusively.

### Step 2: Analyze Hemichordata
- Hemichordata is a phylum that includes acorn worms and pterobranchs.
- These organisms are primarily marine and are found in oceanic environments.
- **Conclusion**: Hemichordata is considered to be exclusively marine.

### Step 3: Analyze Protocordates
- Protocordates are a group that includes organisms like tunicates and lancelets.
- They are predominantly marine animals, living in oceanic waters.
- **Conclusion**: Protocordates are also considered to be exclusively marine.

### Step 4: Evaluate the Options
- Since both Hemichordata and Protocordates are exclusively marine, we need to consider the question's phrasing.
- The question asks for an option that is exclusively marine, and since Hemichordata fits this criterion, it is the correct answer.
- However, if the options include all three groups (Echinodermata, Hemichordata, and Protocordates), then the answer could be interpreted differently.

### Final Answer
- The correct answer is **Hemichordata**, as it is exclusively marine.