Mark the mismatched pair :

Options

A. Dragonfly - Biocontrol agent
B. Oscilatoria - Increase alkalinity of soil
C. Anaerobic sludge digester - Biogas
D. VAM - Biofertiliser

Answer

To solve the question of identifying the mismatched pair from the given options, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Option A: Dragonfly - Biocontrol Agent**
- Dragonflies are known to feed on mosquitoes and other pests. They are indeed used as biocontrol agents to manage pest populations.
- **Conclusion:** This pair is correctly matched.

2. **Option B: Oscillatoria - Increase Alkalinity of Soil**
- Oscillatoria is a type of cyanobacteria (blue-green algae) that plays a significant role in nitrogen fixation. However, it does not increase the alkalinity of the soil. Instead, it helps in enriching the soil with nitrogen.
- **Conclusion:** This pair is mismatched.

3. **Option C: Anaerobic Sludge - Digester, Biogas**
- Anaerobic sludge digesters are used to break down organic matter in the absence of oxygen, leading to the production of biogas, which is rich in methane. This is a correct association.
- **Conclusion:** This pair is correctly matched.

4. **Option D: WAM (Vesicular Arbuscular Mycorrhizae) - Biofertilizer**
- WAM refers to a type of mycorrhizal fungi that forms a symbiotic relationship with plant roots. It helps in nutrient absorption, particularly phosphorus, making it a biofertilizer.
- **Conclusion:** This pair is correctly matched.

### Final Answer:
The mismatched pair is **Option B: Oscillatoria - Increase Alkalinity of Soil**.

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