Water of river Ganges remains 'pure' due to presence of

Options

A. Bacteriophages
B. Cyanophages
C. Bacteria
D. Hydrophytes.

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks why the water of the river Ganges is considered 'pure'. This implies that we need to identify the organism or factor that contributes to the purity of the water.

2. **Analyzing the Options**:
- **Bacteriophages**: These are viruses that infect bacteria. They can reduce bacterial populations but do not directly contribute to water purity.
- **Cyanophages**: These are viruses that specifically infect cyanobacteria. Similar to bacteriophages, they do not contribute to the overall purity of water.
- **Bacteria**: Certain bacteria can play a role in purifying water by breaking down organic matter and competing with harmful bacteria.
- **Hydrophytes**: These are aquatic plants that can help in filtering water but are not the primary reason for the purity of river water.

3. **Identifying the Key Organism**: Research has shown that a specific bacterium known as *Delovibrio bacteriovirus* is crucial in maintaining the purity of the Ganges water. This bacterium preys on other bacteria, thus helping to control bacterial populations and prevent contamination.

4. **Conclusion**: The presence of beneficial bacteria, particularly *Delovibrio bacteriovirus*, is responsible for the purity of the river Ganges. Therefore, the correct answer to the question is "bacteria".

**Final Answer**: The water of river Ganges remains 'pure' due to the presence of bacteria, specifically *Delovibrio bacteriovirus*.

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