Which one is mismatched ?

Options

A. (a) Hydra vulgaris- sea water
B. (b) Hydra gangetica-- fresh water
C. (c) Obelia -sea water
D. (d) Physalia-sea water

Answer

To determine which option is mismatched, we need to analyze each option provided in the question. Here’s a step-by-step breakdown:

### Step 1: Analyze Option A - Hydra vulgaris
- **Description**: Hydra vulgaris is a type of hydra.
- **Habitat**: It is known to inhabit freshwater environments.
- **Conclusion**: The pairing of Hydra vulgaris with seawater is incorrect, as it exclusively lives in freshwater.

### Step 2: Analyze Option B - Hydra gingiatica
- **Description**: Hydra gingiatica is another type of hydra.
- **Habitat**: This species is also found in freshwater, specifically in the Ganga river.
- **Conclusion**: The pairing of Hydra gingiatica with freshwater is correct.

### Step 3: Analyze Option C - Obelia
- **Description**: Obelia is a genus of colonial hydroids.
- **Habitat**: It is commonly found in marine environments (seawater).
- **Conclusion**: The pairing of Obelia with seawater is correct.

### Step 4: Analyze Option D - Piscenia
- **Description**: Piscenia is another organism that is typically found in marine habitats.
- **Habitat**: It is also associated with seawater.
- **Conclusion**: The pairing of Piscenia with seawater is correct.

### Final Conclusion:
After analyzing all options, we find that the mismatched pair is:
- **A**: Hydra vulgaris - seawater (incorrect, as Hydra vulgaris is a freshwater organism).

### Answer:
The mismatched option is **A: Hydra vulgaris with seawater**.

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