In which of the echinoderm, the arms, spines and pedicellaria are absent?

Options

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

Answer

To determine which echinoderm lacks arms, spines, and pedicellaria, we can analyze the given options step by step.

### Step-by-Step Solution:

1. **Identify the Options**: The options provided are:
- A. Sea Cucumber
- B. Sea Lily
- C. Starfish
- D. Sea Urchin

2. **Analyze Option A: Sea Cucumber**:
- Sea Cucumbers belong to the class Holothuroidea.
- Members of this class are characterized by the absence of arms, spines, and pedicellaria.
- Conclusion: Sea Cucumber has no arms, no spines, and no pedicellaria.

3. **Analyze Option B: Sea Lily**:
- Sea Lilies belong to the class Crinoidea.
- They do not have spines or pedicellaria, but they do have branched arms.
- Conclusion: Sea Lily has branched arms, so it does not fit the criteria.

4. **Analyze Option C: Starfish**:
- Starfish belong to the class Asteroidea.
- They possess spines and have five flat arms along with pedicellaria.
- Conclusion: Starfish has arms and spines, so it does not fit the criteria.

5. **Analyze Option D: Sea Urchin**:
- Sea Urchins belong to the class Echinoidea.
- They do not have arms but do have spines and pedicellaria.
- Conclusion: Sea Urchin has spines, so it does not fit the criteria.

6. **Final Conclusion**:
- The only echinoderm from the options that lacks arms, spines, and pedicellaria is **Option A: Sea Cucumber**.

### Answer:
The echinoderm in which the arms, spines, and pedicellaria are absent is **Option A: Sea Cucumber**.

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