Which of the following phylum has closed circulatory system?

Options

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

Answer

To determine which phylum has a closed circulatory system, we will analyze each of the given options step by step.

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are Arthropoda, Annelida, Mollusca, and Echinodermata.

2. **Examine Option A: Arthropoda**:
- Arthropods, such as insects (e.g., grasshoppers), have an open circulatory system.
- In an open circulatory system, blood is not contained within blood vessels but instead flows freely through cavities called hemocoels.
- **Conclusion**: Arthropoda does not have a closed circulatory system.

3. **Examine Option B: Annelida**:
- Annelids, such as earthworms, possess a closed circulatory system.
- In this system, blood is contained within blood vessels, and it is distinct from the interstitial fluid.
- Annelids have a heart that pumps blood through ventral and dorsal blood vessels.
- **Conclusion**: Annelida has a closed circulatory system.

4. **Examine Option C: Mollusca**:
- Mollusks generally have an open circulatory system, with blood flowing through sinuses rather than being confined to vessels.
- **Conclusion**: Mollusca does not have a closed circulatory system.

5. **Examine Option D: Echinodermata**:
- Echinoderms also possess an open circulatory system.
- Their blood is not contained within a closed network of vessels.
- **Conclusion**: Echinodermata does not have a closed circulatory system.

6. **Final Conclusion**:
- The only phylum from the options provided that has a closed circulatory system is **Annelida**.

### Answer:
The phylum that has a closed circulatory system is **Annelida**.