Biogas includes all of the following, except

Options

A. `CH_4`
B. `CO_2`
C. `H_2`
D. CO

Answer

To solve the question regarding the components of biogas, we need to analyze the options provided and understand the composition of biogas.

### Step-by-Step Solution:

1. **Understanding Biogas Composition**:
- Biogas is primarily produced through the anaerobic digestion of organic matter.
- The main components of biogas include methane (CH4) and carbon dioxide (CO2), along with small amounts of other gases.

2. **Analyzing the Options**:
- **Option A: Methane (CH4)**: This is a primary component of biogas, produced by methanogenic microorganisms.
- **Option B: Carbon Dioxide (CO2)**: This is also a significant component of biogas, resulting from the breakdown of organic matter.
- **Option C: Hydrogen (H2)**: Hydrogen can be present in trace amounts in biogas, produced during the anaerobic digestion process.
- **Option D: Carbon Monoxide (CO)**: This gas is not a typical component of biogas and is not produced during the anaerobic digestion of organic waste.

3. **Identifying the Exception**:
- Since methane, carbon dioxide, and hydrogen are all components of biogas, the only gas that does not belong to the composition of biogas is carbon monoxide.

4. **Conclusion**:
- Therefore, the answer to the question "Biogas includes all of the following, except" is **Carbon Monoxide (CO)**.

### Final Answer:
**Carbon Monoxide (CO)**

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