Acid-rain is related to

Options

A. `SO_2 + NO_2`
B. `NO_3`
C. `O_3`
D. `CO`

Explanation

**Step-by-Step Solution:**

1. **Understanding Acid Rain**: Acid rain is precipitation that has a lower pH than normal rainwater. It is primarily caused by the presence of certain pollutants in the atmosphere.

2. **Identifying Key Gases**: The main gases responsible for acid rain are sulfur dioxide (SO2) and nitrogen oxides (NO2). These gases are released into the atmosphere from various sources, including industrial processes and vehicle emissions.

3. **Chemical Reactions**: When SO2 and NO2 are released into the atmosphere, they react with water vapor (H2O) present in the air.
- SO2 reacts with water to form sulfuric acid (H2SO4).
- NO2 reacts with water to form nitric acid (HNO3).

4. **Role of Carbon Dioxide (CO2)**: While carbon dioxide (CO2) is also a gas released into the atmosphere, it forms carbonic acid (H2CO3) when it reacts with water. However, the contribution of CO2 to acid rain is minimal compared to that of SO2 and NO2.

5. **Conclusion**: The gases primarily responsible for acid rain are sulfur dioxide (SO2) and nitrogen oxides (NO2). Therefore, when asked which gases are related to acid rain, the correct answer would be those two.

**Final Answer**: Acid rain is related to sulfur dioxide (SO2) and nitrogen oxides (NO2).

---