Understanding Water Cleaning
Cleaning of water is essential for ensuring its safety and suitability for consumption and other uses. The process involves removing various unwanted substances that may compromise water quality.

What Are Contaminants?
- **Contaminants** refer to any physical, chemical, or biological substances that can degrade water quality.
- They can include a wide range of harmful pollutants such as heavy metals, pesticides, industrial chemicals, and organic matter.

Importance of Removing Contaminants
- Removing contaminants is crucial for:
- **Protecting Health**: Contaminated water can lead to diseases and health issues.
- **Environmental Safety**: Pollutants can harm aquatic ecosystems and biodiversity.
- **Ensuring Potability**: Safe drinking water must be free from harmful substances.

Other Substances in Water Cleaning
While sediments, microorganisms, and bacteria are also removed during water cleaning, the term "contaminants" encompasses a broader category, making it the most appropriate answer.
- **Sediments**: These are solid particles that settle at the bottom but do not necessarily pose a health risk.
- **Microorganisms**: While they can be harmful, they are often a subset of contaminants.
- **Bacteria**: Like microorganisms, bacteria are a specific group that can be harmful but are included within the broader category of contaminants.

Conclusion
In summary, while sediments, microorganisms, and bacteria are important, the term "contaminants" effectively captures the wide range of harmful substances removed during the water cleaning process. This is why option 'B' is the correct answer.