Non-combustible gas is

Options

A. CO
B. `CH_4`
C. `N_2`
D. `C_4H_10`

Explanation

### Step-by-Step Solution:

1. **Understanding Non-Combustible Gases**:
- Non-combustible gases are those that do not easily react with oxygen to produce combustion. This means they do not support burning or do not react readily with oxygen.

2. **Identifying Combustible Gases**:
- Common examples of combustible gases include carbon monoxide (CO), methane (CH4), and butane (C4H10). These gases can easily react with oxygen and produce combustion products like carbon dioxide (CO2) and water (H2O).

3. **Examining Each Gas**:
- **Carbon Monoxide (CO)**: It readily reacts with oxygen to form carbon dioxide (CO2). Therefore, it is a combustible gas.
- **Methane (CH4)**: Being a hydrocarbon, methane also combusts in the presence of oxygen, producing CO2 and H2O.
- **Butane (C4H10)**: Similar to methane, butane is another hydrocarbon that combusts easily with oxygen.
- **Nitrogen (N2)**: Nitrogen has a very strong triple bond between its atoms, making it very stable and non-reactive under normal conditions. It does not readily react with oxygen, thus it is considered a non-combustible gas.

4. **Conclusion**:
- Among the gases listed (CO, CH4, N2, and C4H10), nitrogen (N2) is the only gas that does not support combustion due to its strong triple bond and low reactivity with oxygen. Therefore, nitrogen is the correct answer to the question of which gas is non-combustible.

### Final Answer:
- The non-combustible gas is **Nitrogen (N2)**.

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