Regeneration is best shown by flat worm

Options

A. Fasciola
B. Planaria dugesia
C. Schistosoma
D. Echinococcus

Answer

### Step-by-Step Solution:

1. **Understanding Regeneration**: Regeneration is the biological process through which certain organisms can regrow lost body parts. It involves the ability to replace or restore damaged or lost tissues, organs, or limbs.

2. **Identifying the Organisms**: The question lists several organisms: Fasciola (liver fluke), Planaria (a type of flatworm), Dogastria, Cystostoma (blood fluke), and Echinococcus (dog tapeworm). We need to determine which of these exhibits the best regeneration capabilities.

3. **Analyzing Each Organism**:
- **Fasciola (Liver Fluke)**: While it is a flatworm, it does not have significant regeneration capabilities.
- **Planaria**: This is a well-known flatworm that has remarkable regenerative abilities. If a Planaria is cut into pieces, each piece can regenerate into a complete organism.
- **Cystostoma (Blood Fluke)**: Similar to Fasciola, it does not exhibit notable regeneration.
- **Echinococcus (Dog Tapeworm)**: This organism also does not show significant regenerative abilities.

4. **Conclusion**: Among the listed organisms, Planaria is the one that demonstrates the highest capacity for regeneration. It can regenerate lost body parts effectively, making it the best example of regeneration among flatworms.

5. **Final Answer**: The organism that shows the best regeneration is **Planaria**.