Polluted water do not contain

Options

A. Stone Fly Larvae
B. Sewage fungus
C. Water Hyacinth
D. Cyanobacteria.

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks which organism is not found in polluted water. This requires knowledge of various organisms and their tolerance to water quality.

2. **Analyzing the Options**:
- **Stonefly Larva**: Known to be sensitive to pollution and typically found in clean, flowing water. They are indicators of good water quality.
- **Sewage Fungus**: This organism thrives in polluted water, particularly in areas with high organic waste.
- **Water Hyacinth**: This aquatic plant often grows in nutrient-rich, polluted waters.
- **Cyanobacteria**: Also known as blue-green algae, these can proliferate in polluted waters, especially where there are excess nutrients.

3. **Identifying the Correct Answer**: Since stonefly larvae are sensitive to pollution and are indicators of clean water, they are not found in polluted environments. The other options (sewage fungus, water hyacinth, and cyanobacteria) are commonly found in polluted waters.

4. **Conclusion**: The organism that does not exist in polluted water is the **Stonefly Larva**.

### Final Answer:
**Stonefly Larva**

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