Which of the following gas does not contribute to the formation of acid rain ?

Options

A. nitrogen monoxide
B. carbon monoxide
C. sulphur dioxide
D. nitrogen dioxide

Explanation

To determine which gas does not contribute to the formation of acid rain, we need to analyze the gases mentioned and their reactions with water.

### Step-by-Step Solution:

1. **Understanding Acid Rain**:
Acid rain is formed when certain gases react with water vapor in the atmosphere, leading to the formation of acidic compounds. The most common gases that contribute to acid rain are sulfur dioxide (SO₂) and nitrogen oxides (NOₓ).

2. **Identifying the Gases**:
- **Sulfur Dioxide (SO₂)**: This gas reacts with water to form sulfurous acid (H₂SO₃), which contributes to acid rain.
- **Nitrogen Oxides (NOₓ)**: These gases, including nitrogen dioxide (NO₂), react with water to form nitric acid (HNO₃), also contributing to acid rain.
- **Carbon Monoxide (CO)**: This gas does not react with water to form any acidic compounds.

3. **Analyzing Carbon Monoxide**:
- The reaction of carbon monoxide with water does not produce an acid. Instead, it forms carbon dioxide (CO₂) and hydrogen gas (H₂). The reaction can be represented as:
\[ CO + H₂O \rightarrow CO₂ + H₂ \]
- Since no acid is formed in this reaction, carbon monoxide does not contribute to acid rain.

4. **Conclusion**:
Among the gases listed, carbon monoxide (CO) is the only gas that does not contribute to the formation of acid rain.

### Final Answer:
**Carbon Monoxide (CO)** does not contribute to the formation of acid rain.

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