Which one of these sources of water pollution does not involve any pollutants?

Options

A. Industrial wastewater
B. Domestic wastewater
C. Agricultural run-off
D. Thermal pollution

Explanation

To determine which source of water pollution does not involve any pollutants, we will analyze each option provided:

### Step-by-Step Solution:

1. **Analyze Industrial Wastewater**:
- Industrial wastewater is generated from manufacturing processes and can contain a variety of harmful substances, including organic and inorganic pollutants. If not treated properly, it can significantly contaminate water bodies.
- **Conclusion**: This option involves pollutants.

2. **Analyze Domestic Wastewater**:
- Domestic wastewater comes from household activities and typically contains a mixture of organic matter, microbes, and inorganic substances (like soaps and detergents). These components can lead to water pollution.
- **Conclusion**: This option also involves pollutants.

3. **Analyze Agricultural Runoff**:
- Agricultural runoff occurs when rainwater or irrigation water flows over agricultural fields, carrying with it fertilizers, pesticides, and other chemicals used in farming. These substances can contaminate nearby water sources.
- **Conclusion**: This option involves pollutants as well.

4. **Analyze Thermal Pollution**:
- Thermal pollution is primarily caused by the discharge of heated water from power plants into water bodies. While it does not introduce chemical pollutants, it raises the temperature of the water, which can lead to decreased oxygen levels and affect aquatic life. However, it does not introduce any foreign pollutants into the water.
- **Conclusion**: This option does not involve traditional pollutants.

### Final Answer:
The source of water pollution that does not involve any pollutants is **D. Thermal Pollution**.