Regeneration power can best be studied in

Options

A. Planaria /Dugesia
B. Amphioxus
C. Earthworm
D. Sponge .

Answer

### Step-by-Step Solution:

1. **Understanding Regeneration**: Regeneration is the process by which organisms can regrow lost or damaged parts. It is a significant biological phenomenon that varies among different species.

2. **Identifying the Organism**: The question asks about the organism where regeneration can be best studied. Among various organisms, planarians (a type of flatworm) are known for their remarkable regenerative abilities.

3. **Planarian Characteristics**: Planarians possess a high degree of regeneration power. When a planarian is cut into pieces, each piece can regenerate into a complete organism. This ability is due to the presence of specialized cells called neoblasts.

4. **Mechanism of Regeneration**: When a planarian is cut, the cells at the wound site proliferate to form a structure known as a blastema. The cells in the blastema then differentiate into various types of tissues, allowing the organism to regenerate the missing parts.

5. **Conclusion**: Therefore, the organism in which regeneration power can be best studied is the planarian.

### Final Answer:
Regeneration power can best be studied in **planarians**.

---