Assertion: Animals such as sponge, Planaria, Hydra, can generate the whole body from a part.
Reason: Regeneration is quite common in animals.

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false.
D. If both assertion and reason are false.

Answer

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that animals such as sponges, Planaria, and Hydra can generate a whole body from a part. This is true because these organisms are known for their regenerative abilities. For example, if a Planaria is cut into pieces, each piece can grow into a complete new organism.

2. **Understanding the Reason**:
- The reason states that regeneration is quite common in animals. This statement is misleading. While regeneration does occur in some animals, it is not a common trait across all animal species. Many animals do not have the ability to regenerate lost body parts.

3. **Evaluating the Truth of Each Statement**:
- **Assertion**: True. Animals like sponges, Planaria, and Hydra can regenerate and form a complete organism from a part.
- **Reason**: False. Regeneration is not common in all animals; it is limited to specific species.

4. **Conclusion**:
- Since the assertion is true and the reason is false, the correct relationship is that the assertion stands on its own without the support of the reason. Therefore, the correct answer is that the assertion is true, but the reason is false.

### Final Answer:
- Assertion is true, but reason is false.