An organism used as biofertilizer for raising soyabean crop is
Or
Most famous nitrogen fixing bacterium/biofertilizer is

Options

A. Azospirillum
B. Rhizobium
C. Nostoc
D. Azotobacter

Explanation

To answer the question regarding the organism used as a biofertilizer for raising soybean crops or the most famous nitrogen-fixing bacterium, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Biofertilizers**: Biofertilizers are natural fertilizers that contain living microorganisms. They enhance the availability of nutrients to plants, particularly nitrogen, which is essential for plant growth.

2. **Identifying Nitrogen-Fixing Bacteria**: Nitrogen-fixing bacteria are crucial for converting atmospheric nitrogen into a form that plants can absorb and utilize. This process is vital for crops like soybean, which require a significant amount of nitrogen.

3. **Common Nitrogen-Fixing Bacteria**: Some well-known nitrogen-fixing bacteria include:
- **Rhizobium**: This bacterium forms symbiotic relationships with legumes, including soybeans, and is highly effective in fixing nitrogen.
- **Azospirillum**: This bacterium is also a biofertilizer but is more commonly associated with grasses rather than legumes.
- **Azotobacter**: This free-living bacterium can fix nitrogen but is not specifically linked to soybean crops.
- **Nostoc**: This is a cyanobacterium that can also fix nitrogen but is typically associated with other crops like rice and tea.

4. **Conclusion**: The most famous nitrogen-fixing bacterium used as a biofertilizer for raising soybean crops is **Rhizobium**. It is specifically adapted to form nodules on the roots of soybean plants, facilitating nitrogen fixation.

### Final Answer:
The organism used as a biofertilizer for raising soybean crops is **Rhizobium**.

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