Respiratory organs in a sea star are

Options

A. Ctenidia
B. Book lungs
C. Dermal branchiae
D. madriporite

Answer

### Step-by-Step Solution:

1. **Identify the Organism**: The question asks about the respiratory organs in a sea star, which is also known as a starfish. Sea stars belong to the phylum Echinodermata.

2. **Understand the Respiratory System of Echinoderms**: Echinoderms, including sea stars, have unique respiratory structures. Unlike many other animals, they do not have lungs or gills.

3. **Identify the Specific Respiratory Organ**: The primary respiratory organ in sea stars is called **Dermal Branchiae**. These are small, cilia-like structures that extend from the body surface.

4. **Function of Dermal Branchiae**: Dermal Branchiae facilitate gas exchange. They allow the sea star to take in oxygen and expel carbon dioxide directly through the skin.

5. **Clarify Other Structures**: It's important to note that while other structures like **madreporite** are present in sea stars, they do not serve a respiratory function. The madreporite is involved in the water vascular system and helps in filtering water.

6. **Conclusion**: Therefore, the correct answer to the question is that the respiratory organs in a sea star are **Dermal Branchiae**.