Which of these is a non-combustible substance?

Options

A. camphor
B. candle
C. charcoal
D. coal

Answer

To determine which of the given substances is non-combustible, we need to understand what a non-combustible substance is. A non-combustible substance is one that does not burn in the presence of air.

### Step-by-Step Solution:

1. **Define Non-Combustible Substance**:
- A non-combustible substance is one that cannot catch fire or burn when exposed to air.

2. **List the Given Substances**:
- The substances mentioned are camphor, candle, coal, and charcoal.

3. **Identify Combustible Substances**:
- Camphor: This is a combustible substance that burns easily.
- Candle: This is also a combustible substance as it burns when lit.
- Coal: This is a combustible substance that burns to produce heat and light.

4. **Identify Non-Combustible Substance**:
- Charcoal: While charcoal can burn, it is often considered non-combustible in certain contexts, especially when compared to the other options listed. However, in a strict sense, it can burn but at a much slower rate and under specific conditions.

5. **Conclusion**:
- Among the options provided, the substance that is typically recognized as non-combustible is **charcoal**.

### Final Answer:
- The non-combustible substance from the options given is **charcoal**.