Which among the following is not a fuel?

Options

A. cow dung
B. natural gas
C. coal
D. sodium

Answer

To determine which among the given options is not a fuel, we need to analyze the properties of fuels and the behavior of the substances listed.

### Step-by-Step Solution:

1. **Understanding Fuels**:
- Fuels are substances that react with oxygen to produce energy. Common examples include cow dung, natural gas, and coal.

2. **Identifying the Options**:
- The question presents several options, among which we need to identify the one that is not a fuel.

3. **Analyzing Sodium**:
- Sodium is a metal that reacts vigorously with oxygen. The reaction can be represented as:
\[ 4 \text{Na} + \text{O}_2 \rightarrow 2 \text{Na}_2\text{O} \]
- This reaction releases heat energy, but sodium is not considered a fuel because it does not meet the criteria of a good fuel.

4. **Characteristics of Good Fuels**:
- Good fuels should be:
- Easily available
- Inexpensive
- Burn at a moderate rate (not too fast or too slow)
- Sodium burns too quickly and reacts vigorously, which disqualifies it from being a fuel.

5. **Conclusion**:
- Based on the analysis, sodium does not fulfill the criteria of a fuel. Therefore, the answer to the question is **Sodium**.

### Final Answer:
Sodium is not a fuel.

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