Which is not a bioidicator of water pollution

Options

A. Blood worms
B. Stone flies
C. Sewage fungus
D. Sludge worms.

Answer

To determine which organism is not a bioindicator of water pollution, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Concept of Bioindicators**:
- Bioindicators are organisms that reflect the health of an ecosystem, particularly in terms of pollution levels. They can indicate the presence of contaminants or the quality of the environment.

2. **Analyze the Given Options**:
- The options provided are:
- A) Blood worms
- B) Stone flies
- C) Sewage fungus
- D) Sludge worms

3. **Evaluate Each Option**:
- **Blood Worms**: These are known to thrive in polluted waters, particularly in environments with low oxygen levels, making them bioindicators of water pollution.
- **Stone Flies**: These organisms are sensitive to pollution and can only survive in clean, unpolluted waters. Their presence indicates good water quality, not pollution.
- **Sewage Fungus**: This fungus grows in polluted waters and is a clear indicator of organic pollution.
- **Sludge Worms**: Similar to blood worms, sludge worms can survive in low-oxygen environments and are indicative of pollution.

4. **Identify the Correct Answer**:
- Based on the evaluations, the only organism that does not indicate water pollution is **B) Stone flies**. They are found in clean waters and their presence signifies good water quality.

5. **Conclude the Answer**:
- Therefore, the organism that is not a bioindicator of water pollution is **Stone flies**.

### Final Answer:
**B) Stone flies**