Metamerism is a characteristic of

Options

A. Ascaris
B. Pheretima
C. Periplaneta
D. Hydra

Answer

### Step-by-Step Solution:

1. **Understanding Metamerism**:
- Metamerism is a biological phenomenon where the body of an organism is divided into repeated segments, known as metamers. Each segment can have similar structures and functions.

2. **Identifying the Phylum**:
- Metamerism is primarily observed in the phylum Annelida, which includes segmented worms. This segmentation is both external (visible grooves) and internal (corresponding organs).

3. **Analyzing the Options**:
- **A. Ascaris**: This organism belongs to the phylum Nematoda (roundworms) and does not exhibit true segmentation.
- **B. Ferritima**: This organism belongs to the phylum Annelida (segmented worms) and is characterized by metamerism.
- **C. Periplaneta**: This is a cockroach, which belongs to the phylum Arthropoda. Arthropods do not exhibit true metamerism as seen in annelids.
- **D. Hydra**: This organism belongs to the phylum Cnidaria and does not show metamerism.

4. **Conclusion**:
- Based on the analysis, the only organism that exhibits metamerism is **Ferritima**, which is a representative of the Annelida phylum.

5. **Final Answer**:
- The correct answer is **B. Ferritima**.