Main pollutant from automobile exhaust is :

Options

A. `CO`
B. `CO_(2)`
C. `NO`
D. hydrocarbons

Explanation

To determine the main pollutant from automobile exhaust, we can analyze the options provided:

1. **Carbon Monoxide (CO)**: This is a colorless, odorless gas that is produced when carbon-containing fuels are burned incompletely. In the context of automobiles, this occurs when there is insufficient oxygen for complete combustion.

2. **Carbon Dioxide (CO2)**: This is a greenhouse gas produced during the complete combustion of carbon-containing fuels. While it is a significant emission from vehicles, it is not considered a primary pollutant in the same way as carbon monoxide.

3. **Nitric Oxide (NO)**: This gas is produced during combustion processes, especially at high temperatures, and is a contributor to air pollution. However, it is not the main pollutant from automobile exhaust.

4. **Hydrocarbons**: These are organic compounds made up of hydrogen and carbon. They can be emitted from vehicles, particularly from unburned fuel, but they are not the primary pollutant.

### Step-by-Step Solution:

**Step 1**: Identify the pollutants emitted from automobile exhaust.
- The main pollutants include carbon monoxide (CO), carbon dioxide (CO2), nitric oxide (NO), and hydrocarbons.

**Step 2**: Understand the formation of each pollutant.
- **Carbon Monoxide (CO)**: Formed due to incomplete combustion of fossil fuels.
- **Carbon Dioxide (CO2)**: Formed during complete combustion of fossil fuels.
- **Nitric Oxide (NO)**: Formed at high temperatures during combustion.
- **Hydrocarbons**: Emitted from unburned fuel.

**Step 3**: Determine which pollutant is produced in the highest quantity from automobile exhaust.
- Carbon monoxide is produced significantly due to incomplete combustion, especially in urban areas with heavy traffic.

**Step 4**: Conclude which is the main pollutant.
- Based on the analysis, the main pollutant from automobile exhaust is carbon monoxide (CO).

### Final Answer:
The main pollutant from automobile exhaust is **Carbon Monoxide (CO)**.