The only segmented mollusca is

Options

A. Neopilina
B. Teredo
C. Nautilus
D. Chiton

Answer

To answer the question "The only segmented mollusca is," we will go through the options provided and identify the correct answer step by step.

### Step-by-Step Solution:

1. **Understanding the Question**:
The question asks for the only segmented mollusca. Segmentation is a characteristic feature of certain animal phyla, notably Annelida (segmented worms). We need to find out which mollusca exhibits segmentation.

2. **Analyzing the Options**:
- **A. Neoplina**: This is known to be a segmented mollusc. It has a unique structure that shows segmentation, making it a candidate for our answer.
- **B. Terepto**: This is not recognized as a segmented mollusc. It belongs to a group of molluscs that do not exhibit segmentation.
- **C. Nautilus**: This is a cephalopod mollusc and does not show segmentation. It has a coiled shell and is not segmented.
- **D. Chiton**: Chitons have a shell made up of eight plates but are not segmented in the same way as Annelids.

3. **Identifying the Correct Answer**:
After analyzing the options, we find that **Neoplina** is the only segmented mollusc among the choices given. It has a distinct body structure that includes segmentation, which is not found in the other options.

4. **Conclusion**:
Therefore, the answer to the question is **A. Neoplina**.

### Final Answer:
The only segmented mollusca is **A. Neoplina**.