Fires in underground coal mines usually occur due to the :

Options

A. explosive combustion
B. deliberate combustion
C. spontaneous combustion
D. rapid combustion

Answer

**Step-by-Step Solution:**

1. **Understanding the Context**: The question asks about the cause of fires in underground coal mines. To answer this, we need to explore the types of combustion that could occur in such an environment.

2. **Identifying Types of Combustion**: There are several types of combustion:
- **Spontaneous Combustion**: This occurs when a material catches fire without an external ignition source.
- **Rapid Combustion**: This is a fast process that produces heat, light, and sound, typically requiring an external source of ignition.
- **Deliberate Combustion**: This is a controlled and slow process of burning.
- **Explosive Combustion**: This is a very rapid combustion that results in an explosion.

3. **Analyzing the Most Likely Cause**: In the context of underground coal mines, the most relevant type of combustion is spontaneous combustion. This is because coal can heat up due to oxidation and can ignite without any external flame or spark.

4. **Conclusion**: Based on the analysis, the fires in underground coal mines usually occur due to **spontaneous combustion**.

5. **Final Answer**: The correct answer is spontaneous combustion.

---