The calcareous ossicles in echinoderms form the

Options

A. Exoskeleton
B. Visceral hump
C. Notochord
D. Endoskeleton

Explanation

**Step-by-Step Solution:**

1. **Identify the Organism**: The question refers to echinoderms, which belong to the phylum Echinodermata. This group includes marine animals such as starfish, sea urchins, and sea cucumbers.

2. **Understand the Structure**: Echinoderms have a unique body structure that includes calcareous (calcium carbonate) components. These components are important for their skeletal system.

3. **Differentiate Between Skeleton Types**: Echinoderms possess two types of skeletons:
- **Exoskeleton**: This is an external skeleton that provides support and protection. In echinoderms, the spines on the skin are part of this structure.
- **Endoskeleton**: This is an internal skeleton that provides support from within. In echinoderms, the endoskeleton is made up of calcareous plates known as ossicles.

4. **Determine the Role of Ossicles**: The calcareous ossicles are specifically part of the endoskeleton in echinoderms. They provide structural support and play a role in the overall shape and function of the organism.

5. **Select the Correct Option**: Based on the understanding that calcareous ossicles form the endoskeleton, the correct answer to the question is that the calcareous ossicles in echinoderms form the endoskeleton.

**Final Answer**: The calcareous ossicles in echinoderms form the endoskeleton.

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