The advantage of ploughing is that it

Options

A. allows the penetration of roots of plants
B. helps in proper aeration and eradicates weeds
C. promotes the growth of useful soil bacteria
D. all of these

Explanation

**Step-by-Step Solution:**

1. **Understanding Ploughing**: Ploughing is the agricultural practice of turning over the upper layer of soil. This process helps to prepare the soil for planting by mixing it and aerating it.

2. **Loosening the Soil**: When the soil is ploughed, it becomes loose. This looseness is essential for the penetration of plant roots. Roots need a soft and aerated environment to grow effectively.

3. **Facilitating Root Penetration**: The primary advantage of ploughing is that it allows for the penetration of roots into the soil. Loose soil enables roots to spread out and access nutrients and water more easily.

4. **Improving Aeration**: Ploughing enhances the aeration of the soil. Proper aeration is crucial for the exchange of gases, which supports the growth of plants and the health of soil microorganisms.

5. **Eradicating Weeds**: During the ploughing process, weeds are uprooted and mixed into the soil. This helps in controlling weed growth, which can compete with crops for nutrients and water.

6. **Promoting Beneficial Microorganisms**: Ploughing also promotes the growth of beneficial soil bacteria, such as nitrogen-fixing bacteria. These bacteria are essential for enriching the soil with nutrients that are vital for plant growth.

7. **Conclusion**: In summary, the advantages of ploughing include enabling root penetration, improving soil aeration, eradicating weeds, and promoting the growth of beneficial soil bacteria.