The green colour of Hydra viridis (Chlorohydra viridissima) is due to

Options

A. Chloroplasts
B. Pigment
C. Zoochlorella
D. None of the above.

Answer

**Step-by-Step Solution:**

1. **Identify the Organism**: The question refers to Hydra viridis, also known as Chlorohydra viridissima.

2. **Understand the Coloration**: The green color of Hydra viridis is a key aspect of this question.

3. **Determine the Cause of Color**: The green color is due to the presence of a specific type of green algae that lives in symbiosis with Hydra viridis.

4. **Identify the Algae**: This green algae is known as zoochlorella. It is responsible for the green coloration by providing chlorophyll, which is the pigment that gives plants their green color.

5. **Evaluate the Options**:
- **Chloroplast**: Incorrect, as chloroplasts are not present in Hydra viridis.
- **Pigment**: Incorrect, as no specific pigment is identified that causes the green color.
- **Zoochlorella**: Correct, as this is the green algae that imparts the green color to Hydra viridis.
- **None of the above**: Incorrect, since we have identified a correct answer.

6. **Conclusion**: The correct answer is Zoochlorella, as it is the green algae that provides the green color to Hydra viridis.

**Final Answer**: Zoochlorella

---