Which of the following is the main factor of desertification?

Options

A. Tourism
B. Irrigated agriculture
C. Over grazing
D. All of these

Explanation

### Step-by-Step Solution:

1. **Understanding Desertification**:
- Desertification is the process by which fertile land becomes increasingly arid and unproductive, often leading to the formation of deserts. It is a significant environmental issue that affects ecosystems and human livelihoods.

2. **Identifying Causes of Desertification**:
- There are several factors that contribute to desertification. The most notable ones include:
- **Deforestation**: The removal of trees and vegetation, which can lead to soil erosion and loss of soil fertility.
- **Overgrazing**: When livestock graze excessively on vegetation, it prevents regrowth and can lead to soil degradation.
- **Human Activities**: Various activities such as agriculture, urbanization, and industrialization can also lead to desertification.

3. **Analyzing the Options**:
- The question provides multiple options regarding the main factor of desertification. We need to evaluate each option based on the causes identified.
- Among the options, overgrazing is highlighted as a significant contributor to desertification due to its direct impact on vegetation and soil health.

4. **Conclusion**:
- After analyzing the causes and the options provided, the main factor of desertification is identified as **overgrazing**. This is because it directly leads to the depletion of vegetation, which is crucial for maintaining soil health and preventing erosion.

5. **Final Answer**:
- The correct answer is **Option 3: Overgrazing**.