In echinoderms, the excretory organs are

Options

A. Protonephridia
B. Absent
C. organs of bojanus
D. kidneys

Answer

### Step-by-Step Solution:

1. **Understanding Echinoderms**: Echinoderms are a group of marine animals that include starfish, sea urchins, and sea cucumbers. They belong to the phylum Echinodermata.

2. **Excretory Organs in Echinoderms**: In Echinoderms, traditional excretory organs, like kidneys, are absent. This means they do not have specialized organs for excreting waste.

3. **Excretion Process**: Instead of having complex excretory systems, Echinoderms excrete waste materials through a simpler process known as diffusion. This occurs primarily through their skin.

4. **Comparison with Other Organisms**:
- **Protonephridia**: This is the excretory system found in flatworms (Platyhelminthes).
- **Organ of Bojanus**: This is the excretory organ in mollusks, often referred to as the kidney.
- **Kidneys in Other Animals**: Mammals and chordates have complex kidneys for excretion.

5. **Conclusion**: Since Echinoderms lack specialized excretory organs and rely on diffusion through their skin for waste removal, we conclude that the excretory organs in Echinoderms are essentially absent.

### Final Answer:
In Echinoderms, the excretory organs are absent; they excrete waste through diffusion via their skin.

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