In which class, arms are absent ?

Options

A. Asteroidea
B. Echinoidea
C. Holothuroidea
D. Holothuroidea and Echinoidea

Answer

To answer the question "In which class, arms are absent?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Context**: The question is about the presence or absence of arms in a specific class of animals within the phylum Echinodermata.

2. **Identify the Phylum**: Echinodermata is a phylum that includes marine animals such as sea stars, sea urchins, and sea cucumbers.

3. **Classify Echinoderms**: Echinoderms are divided into different classes, including:
- Asteroidea (sea stars)
- Echinoidea (sea urchins)
- Holothuroidea (sea cucumbers)

4. **Analyze the Classes**:
- **Asteroidea**: This class has arms (e.g., sea stars).
- **Echinoidea**: This class also has arms (e.g., sea urchins).
- **Holothuroidea**: This class includes sea cucumbers, which are noted for lacking arms.

5. **Identify the Exception**: While most Echinoderms have arms, the Holothuroidea class, specifically the sea cucumber (e.g., C. cucumber), is characterized by the absence of arms.

6. **Conclusion**: The class in which arms are absent is Holothuroidea.

### Final Answer:
The class in which arms are absent is **Holothuroidea**.

---