One of the following is not an exhaustible source of energy . This one is :

Options

A. Natural gas
B. petroleum gas
C. coal gas
D. biogas

Answer

To determine which of the following is not an exhaustible source of energy, we need to analyze each option provided: natural gas, petroleum gas, coal gas, and biogas.

### Step-by-Step Solution:

1. **Understanding Exhaustible vs. Non-Exhaustible Sources**:
- Exhaustible sources of energy are those that can be depleted or used up, such as fossil fuels (coal, petroleum, and natural gas).
- Non-exhaustible sources of energy are those that can be replenished naturally and are not likely to run out, such as solar energy, wind energy, and biogas.

2. **Analyzing the Options**:
- **Natural Gas**: This is a fossil fuel that is formed from the remains of ancient marine organisms. It is found underground and can be depleted with use.
- **Petroleum Gas**: This is derived from crude oil through refining processes. Like natural gas, it is also a fossil fuel and can be exhausted.
- **Coal Gas**: This is produced from coal, which is another fossil fuel. It is also an exhaustible source of energy.
- **Biogas**: This is produced from the anaerobic digestion of organic matter, primarily from waste materials. It is generated from human activities and organic waste, making it a renewable resource.

3. **Conclusion**:
- Among the options provided, biogas is not an exhaustible source of energy because it is continuously produced from organic waste, which is generated by human activities. Therefore, the correct answer is **biogas**.

### Final Answer:
**Biogas is not an exhaustible source of energy.**

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