Which of the following is respiratory organ of Sepia?

Options

A. Ctenidia
B. Gills
C. Tracheae
D. Book lungs

Explanation

**Step-by-Step Solution:**

1. **Identify the Organism**: The question asks about the respiratory organ of Sepia. Sepia is a genus of cuttlefish, which belongs to the phylum Mollusca.

2. **Understand the Phylum**: Sepia is part of the Mollusca phylum, which is known for its diverse range of organisms. The general characteristics of mollusks include a body divided into three parts: the head, the muscular foot, and the visceral mass (or hump).

3. **Identify the Respiratory Organ**: In mollusks, the primary respiratory organs are called "ctenidia," which are gill-like structures that facilitate gas exchange.

4. **Evaluate the Options**: The options provided include:
- A) Ctenidia
- B) Gills
- C) Trachea
- D) Book lungs

Among these, ctenidia is the correct term for the respiratory structure in Sepia.

5. **Eliminate Incorrect Options**:
- Gills are primarily associated with fish.
- Trachea is a respiratory structure found in insects.
- Book lungs are found in some arachnids, such as spiders and scorpions.

6. **Conclude the Answer**: Based on the information and the elimination of incorrect options, the respiratory organ of Sepia is **Ctenidia**.

**Final Answer**: The respiratory organ of Sepia is **Ctenidia**.

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