Which of the following act as biofertilizers

Options

A. Blue-green algae
B. Green algae
C. Yellow algae
D. Red algae

Answer

**Step-by-Step Solution:**

1. **Understanding Biofertilizers:**
- Biofertilizers are substances that contain living microorganisms which promote plant growth by increasing the availability of nutrients in the soil. They help in maintaining the nutrient cycle and restoring depleted nutrients.

2. **Identifying Types of Algae:**
- The question provides four types of algae: blue green alga, green alga, yellow alga, and red alga. We need to determine which of these can act as biofertilizers.

3. **Analyzing Blue Green Alga:**
- Blue green algae, also known as cyanobacteria, are prokaryotic organisms and are commonly used as biofertilizers. They help in nitrogen fixation and nutrient restoration in the soil. Examples include Anabaena and Nostoc.

4. **Analyzing Green Alga:**
- Green algae are eukaryotic organisms and do not function as biofertilizers. They do not have the same capabilities as cyanobacteria in terms of nutrient cycling.

5. **Analyzing Yellow Alga:**
- Yellow algae are also a form of green algae and, like green algae, they are eukaryotic and do not act as biofertilizers.

6. **Analyzing Red Alga:**
- Red algae (Rhodophyceae) are another group of eukaryotic organisms that do not function as biofertilizers. They are primarily used for other purposes, such as food and industrial applications.

7. **Conclusion:**
- Based on the analysis, the only organism from the options that acts as a biofertilizer is the blue green alga (cyanobacteria).

**Final Answer:**
- The correct option is **blue green alga**.

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