Arms, pedicellariae and spines are absent in the echinoderm

Options

A. Sea cucumber
B. Sea lily
C. Sea star
D. Sea urchin

Answer

To solve the question regarding which echinoderm lacks arms, pedicellariae, and spines, we can follow these steps:

### Step-by-Step Solution:

1. **Understand Echinoderms**: Echinoderms are a group of marine animals that include starfish, sea urchins, sea cucumbers, and sea lilies. They are characterized by their radial symmetry and a calcareous endoskeleton.

2. **Identify Key Features**: The question specifically asks for an echinoderm that lacks three features: arms, pedicellariae, and spines.

3. **Examine Examples**:
- **Sea Star (Starfish)**: Sea stars have arms and spines, and they also possess pedicellariae. Therefore, they do not fit the criteria.
- **Sea Cucumber**: Sea cucumbers belong to the class Holothuroidea and are known for having no arms, no spines, and no pedicellariae. This makes them a strong candidate.
- **Sea Lily**: Sea lilies have branched arms but do not have spines or pedicellariae. Thus, they do not meet the criteria since they have arms.
- **Sea Urchin**: Sea urchins do not have arms but do have spines and pedicellariae, so they also do not fit the criteria.

4. **Conclusion**: After analyzing the examples, the only echinoderm that lacks arms, pedicellariae, and spines is the **sea cucumber**.

### Final Answer:
The echinoderm that lacks arms, pedicellariae, and spines is the **sea cucumber**.

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