Which does not cause pollution?

Options

A. Thermal power plant
B. Hydro-electric plant
C. Nuclear power plant
D. Automobiles

Answer

To determine which option does not cause pollution, let's analyze each of the given options step by step:

1. **Thermal Power Plant**:
- Thermal power plants generate electricity by burning fossil fuels such as coal, oil, or natural gas.
- The combustion process releases pollutants into the atmosphere, including carbon dioxide (CO2), sulfur dioxide (SO2), and particulate matter (ash).
- **Conclusion**: Thermal power plants do cause pollution.

2. **Hydroelectric Power Plant**:
- Hydroelectric power plants generate electricity by harnessing the energy of flowing water, typically from rivers or dams.
- This process does not involve burning fossil fuels or releasing harmful emissions into the atmosphere.
- **Conclusion**: Hydroelectric power plants do not cause pollution.

3. **Nuclear Power Plant**:
- Nuclear power plants generate electricity through nuclear fission, which does not produce air pollutants like CO2 or SO2.
- However, they do produce radioactive waste, which is hazardous and poses significant environmental and health risks if not managed properly.
- **Conclusion**: Nuclear power plants do cause pollution in the form of hazardous waste.

4. **Automobiles**:
- Automobiles run on internal combustion engines that burn gasoline or diesel fuel.
- This process releases harmful gases such as carbon monoxide (CO), nitrogen oxides (NOx), and particulate matter into the atmosphere.
- **Conclusion**: Automobiles do cause pollution.

After analyzing all options, we find that the **hydroelectric power plant** is the only option that does not cause pollution.

### Final Answer:
The option that does not cause pollution is **hydroelectric power plant**.

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