Attached echinoderms occurs in class

Options

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

Answer

To determine which class of echinoderms contains attached species, we will analyze the options provided and identify the characteristics of each class.

### Step-by-Step Solution:

1. **Identify the Classes of Echinoderms**:
- The options given are Echinoidea, Holothuroidea, Asteroidea, and Crinoidea.

2. **Examine Each Class**:
- **Echinoidea**: This class includes sea urchins, which are free-swimming and not attached to the substrate.
- **Holothuroidea**: This class includes sea cucumbers. Some species in this class can be attached to the substrate.
- **Asteroidea**: This class includes starfish, which are also free-swimming and not attached.
- **Crinoidea**: This class includes crinoids (or feather stars), which can be attached to the substrate but are generally considered free-swimming.

3. **Determine the Correct Class**:
- Among the classes, Holothuroidea is known for having species that can be attached to the substrate. Therefore, it is the class that contains attached echinoderms.

4. **Conclusion**:
- The correct answer is Holothuroidea (option 2), as it includes the only class of echinoderms that can be attached to the substrate.

### Final Answer:
The attached echinoderms occur in the class **Holothuroidea**.

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