The microbe that increases soil fertilities is:

Options

A. Rhizobium
B. Lactobacillus
C. Yeast
D. Streptococcus

Explanation

**Step-by-Step Solution:**

1. **Identify the Question**: The question asks which microbe increases soil fertility.

2. **Consider the Options**: The options provided include:
- Rhizobium
- Lactobacillus
- Yeast
- Tryptococcus

3. **Analyze Each Option**:
- **Rhizobium**: This is a type of bacteria found in the soil. It is known for its ability to fix atmospheric nitrogen, converting it into a soluble form that plants can absorb. This process enriches the soil with nitrogen, which is essential for plant growth and increases soil fertility.
- **Lactobacillus**: This bacterium is primarily involved in the fermentation process, converting milk into curd. It does not contribute to soil fertility.
- **Yeast**: Yeast is used in fermentation processes, such as in the production of beer and wine. It does not play a role in enhancing soil fertility.
- **Tryptococcus**: This bacterium is associated with diseases and does not have any beneficial impact on soil fertility.

4. **Conclusion**: Based on the analysis, the microbe that increases soil fertility is **Rhizobium**.

5. **Final Answer**: The correct answer is **Rhizobium**.

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