Sponges respire through :-

Options

A. Gills
B. Lungs
C. Book-gills
D. General body surface

Answer

**Step-by-Step Solution:**

1. **Understanding Sponges**: Sponges belong to the phylum Porifera. They are simple aquatic animals known for their porous bodies.

2. **Water Canal System**: Sponges possess a unique water canal system that facilitates various functions including respiration, nutrition, and excretion.

3. **Ostea**: Water enters the sponge through small openings on their surface called ostea. These pores allow water to flow into the sponge.

4. **Spongocoel**: Once the water enters through the ostea, it moves into a central cavity known as the spongocoel.

5. **Osculum**: After circulating through the spongocoel, the water exits the sponge through a larger opening called the osculum.

6. **Gaseous Exchange**: The movement of water through the sponge allows for gaseous exchange (respiration) to occur. Oxygen is absorbed, and carbon dioxide is expelled through the water.

7. **Conclusion**: Given the options (gills, lungs, book gills, general body surface), the correct answer is that sponges respire through their general body surface, specifically through the pores (ostea) that facilitate water flow.

**Final Answer**: Sponges respire through the general body surface (option D).

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