Which of the following does not cause acid rain?

Options

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

Answer

To determine which of the following does not cause acid rain, we first need to understand what acid rain is and what substances contribute to its formation.

### Step-by-Step Solution:

1. **Understanding Acid Rain**:
- Acid rain is defined as rainwater that has a pH lower than 5.6. This lower pH is primarily caused by the presence of acids in the rainwater.

2. **Identifying Common Causes of Acid Rain**:
- The main contributors to acid rain are gases such as sulfur dioxide (SO₂), nitrogen oxides (NOₓ), and carbon dioxide (CO₂).
- When these gases are released into the atmosphere, they can react with water vapor to form acids:
- Sulfur dioxide reacts with oxygen and water to form sulfuric acid (H₂SO₄).
- Nitrogen oxides react with water to form nitric acid (HNO₃).
- Carbon dioxide reacts with water to form carbonic acid (H₂CO₃).

3. **Analyzing the Options**:
- If the question provides options such as sulfur dioxide, nitrogen dioxide, carbon dioxide, and carbon monoxide, we need to identify which of these does not contribute to acid rain.
- Sulfur dioxide, nitrogen dioxide, and carbon dioxide all contribute to acid rain formation as explained above.

4. **Identifying the Correct Answer**:
- Carbon monoxide (CO) does not react with water to form an acid and therefore does not contribute to acid rain.

### Conclusion:
- The substance that does not cause acid rain is **carbon monoxide (CO)**.