The green alga rich in proteins used as food supplements even by space travellers is

Options

A. Chlamydomonas
B. Volvox
C. Spirogyra
D. Chlorella

Answer

To solve the question regarding which green alga is rich in proteins and used as a food supplement by space travelers, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Options**: We have four options to consider:
- A) Chlamydomonas
- B) Volvox
- C) Spirogyra
- D) Chlorella

2. **Understand the Characteristics of Each Option**:
- **Chlamydomonas**: A unicellular green alga, known for its motility and presence in freshwater.
- **Volvox**: A colonial green alga that forms spherical colonies, also found in freshwater.
- **Spirogyra**: A filamentous green alga characterized by spiral chloroplasts, commonly found in freshwater.
- **Chlorella**: A unicellular green alga that is known for its high protein content and is often used as a dietary supplement.

3. **Evaluate Protein Content**: The question specifically asks for an alga that is rich in proteins:
- Chlorella is known to contain about 30% protein, making it one of the richest sources of protein among algae.

4. **Consider Usage in Space Travel**: Chlorella is recognized for its nutritional value and has been used as a food supplement, including by astronauts during space missions due to its high protein and nutrient content.

5. **Conclusion**: Based on the analysis, the correct answer is:
- **D) Chlorella**

### Final Answer:
The green alga rich in proteins used as food supplements even by space travelers is **Chlorella**.