Thermal power plants are one of the causes of air pollution. ______.

Explanation

**Step-by-Step Solution:**

1. **Understanding Thermal Power Plants**: Thermal power plants generate electricity by converting heat energy, usually from burning fossil fuels such as coal, oil, or natural gas.

2. **Emission of Heat and Gases**: During the process of generating electricity, a significant amount of heat is produced. This heat leads to the release of various gases into the atmosphere.

3. **Types of Pollutants Released**: The smoke emitted from thermal power plants primarily contains carbon dioxide (CO2), which is a greenhouse gas. Additionally, carbon monoxide (CO) is also produced, albeit in smaller quantities.

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