Which causes water pollution?

Options

A. Jet planes
B. Herbicides
C. Smoke
D. Combustion of fossils

Answer

### Step-by-Step Solution:

1. **Understanding Water Pollution**: Water pollution is defined as the entry of unwanted substances into water bodies (like rivers, lakes, and oceans), which can harm aquatic life and make water unsafe for human use.

2. **Identifying Options**: The options given are:
- Jet planes
- Heavy sides
- Smoke
- Combustion of fossils

3. **Analyzing Each Option**:
- **Jet Planes**: The fuel used in jet planes (jet aviation fuel) primarily produces carbon dioxide upon combustion. It does not directly contaminate water bodies, so it is not a cause of water pollution.
- **Heavy Sides**: This term seems unclear, but if it refers to heavy metals or heavy machinery, they can contribute to water pollution, but this is not explicitly stated in the options.
- **Smoke**: Smoke is primarily an air pollutant. While it can lead to acid rain, which may indirectly affect water bodies, it is not a direct cause of water pollution.
- **Combustion of Fossils**: The combustion of fossil fuels primarily results in air pollutants (like carbon monoxide and carbon dioxide) and does not directly cause water pollution.

4. **Identifying the Correct Cause**: The question implies that we need to find a direct cause of water pollution. The options provided do not include common direct pollutants like pesticides or herbicides, but herbicides are mentioned in the context of their impact on water when used in agriculture.

5. **Conclusion**: Among the options provided, herbicides are the most relevant to water pollution because they can leach into water supplies when used in farming, thus contaminating water bodies.

### Final Answer:
The correct option that causes water pollution is **herbicides**.

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