An alga which can be employed as food for human being is

Options

A. polysiphonia
B. Ulothrix
C. Chlorella
D. Spirogyra

Answer

To answer the question, "An alga which can be employed as food for human beings is," we will analyze the options provided: polysiphonia, eulothrix, chlorella, and spirogyra.

### Step-by-Step Solution:

1. **Identify the Options**:
- **Polysiphonia**: This is a type of red algae. While it is used in food products (like agar), it is not typically consumed directly as food by humans.
- **Eulothrix**: This is a green alga, but it is not known to be consumed as food by humans.
- **Chlorella**: This is a green alga that is known for its high protein content and is often marketed as a health supplement and food source for humans.
- **Spirogyra**: This is also a green alga, but it is mainly used in research and has medicinal properties rather than being a food source.

2. **Evaluate the Characteristics of Chlorella**:
- Chlorella belongs to the phylum Chlorophyta.
- It performs photosynthesis and contains chlorophyll A and B.
- It is spherical in shape and ranges from 2 to 10 micrometers in diameter.
- Chlorella multiplies rapidly and is rich in essential nutrients.

3. **Nutritional Value of Chlorella**:
- Approximately 45% protein.
- About 20% fat.
- Around 20% carbohydrates.
- Contains 5% fiber and 10% minerals and vitamins.
- It is also abundant in calories and vitamins, making it a potential food source.

4. **Conclusion**:
- Based on the analysis, **Chlorella** is the correct answer as it is the only alga among the options that can be employed as food for human beings.

### Final Answer:
The alga which can be employed as food for human beings is **Chlorella**.