Which of the following considered as biofertilizer :-

Options

A. Bacillus
B. Polyporus
C. Selaginella
D. Azotobacter

Answer

To determine which of the given options is considered a biofertilizer, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Understanding Biofertilizers**:
- Biofertilizers are living organisms that enhance the fertility of the soil by increasing the availability of nutrients to plants. They can fix atmospheric nitrogen, decompose organic matter, or promote plant growth.

2. **Analyzing the Options**:
- **Option 1: Azotobacter**:
- Azotobacter is a free-living, aerobic, rod-shaped soil bacterium.
- It is known for its ability to fix atmospheric nitrogen into a usable form (ammonia) for plants.
- Since it contributes to soil fertility, Azotobacter is considered a biofertilizer.

- **Option 2: Bacillus**:
- Bacillus species are known for their role in denitrification, which means they convert nitrates back into nitrogen gas, releasing it into the atmosphere.
- This process reduces the nitrogen content in the soil, thus it does not enhance soil fertility. Therefore, Bacillus is not a biofertilizer.

- **Option 3: Polysporus**:
- Polysporus is a type of fungus that is used to produce single-cell protein.
- It does not provide essential nutrients or minerals to the soil, so it cannot be classified as a biofertilizer.

- **Option 4: Selaginella**:
- Selaginella is a type of fern, primarily used as an ornamental plant.
- It does not contribute to soil fertility, making it unsuitable as a biofertilizer.

3. **Conclusion**:
- After analyzing all the options, the only organism that qualifies as a biofertilizer is **Azotobacter**.

### Final Answer:
**Azotobacter** is considered a biofertilizer.

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