Mollusc group without radula is

Options

A. Gastrpoda
B. Monoplacphora
C. Bivalvia
D. Cephalopoda

Answer

To determine which group of molluscs lacks a radula, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Mollusc Phylum**: The phylum Mollusca includes various classes such as Gastropoda, Monoplacophora, Bivalvia, and Cephalopoda.

2. **Define Radula**: The radula is a specialized feeding organ found in many molluscs, which is used to scrape or cut food before ingestion.

3. **Identify the Classes**:
- **Gastropoda**: This class includes snails and slugs, which possess a radula for feeding.
- **Monoplacophora**: This class also has a radula.
- **Bivalvia**: This class includes clams, oysters, and mussels, which do not have a radula.
- **Cephalopoda**: This class includes squids and octopuses, which do have a radula.

4. **Focus on Bivalvia**: Among the classes mentioned, Bivalvia is unique because it lacks a radula. Instead, members of this class are filter feeders, meaning they obtain their food by filtering organic matter and small organisms from water.

5. **Conclusion**: Therefore, the mollusc group without a radula is **Bivalvia**.

### Final Answer:
The mollusc group without a radula is **Bivalvia**.

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