Which is a balancing organ of fish :-

Options

A. Ampulla of lorenzini
B. Utriculus
C. Air bladder
D. Internal ear

Answer

To determine the balancing organ of fish, we can analyze the provided options step by step.

### Step-by-Step Solution:

1. **Understanding the Question**: We need to identify which organ in fish is responsible for balance.

2. **Evaluating Option A - Ampullae of Lorenzini**:
- These are specialized sensory organs found in cartilaginous fish (like sharks and rays).
- They are primarily used for detecting electric fields in the water, not for balance.
- **Conclusion**: This option is incorrect.

3. **Evaluating Option B - Eutricholus**:
- This structure is involved in detecting linear accelerations.
- While it has a role in sensing movement, it is not specifically the organ responsible for balance.
- **Conclusion**: This option is also incorrect.

4. **Evaluating Option C - Earplatter**:
- The earplatter (or otoliths) helps in providing buoyancy and is involved in hearing.
- However, it does not serve as the primary balancing organ.
- **Conclusion**: This option is incorrect.

5. **Evaluating Option D - Inner Ear**:
- The inner ear contains structures such as the semicircular canals and otoliths, which are crucial for maintaining balance and spatial orientation in fish.
- This is the correct organ responsible for balance in fish.
- **Conclusion**: This option is correct.

### Final Answer:
The balancing organ of fish is the **Inner Ear** (Option D).