Air bladder in a fish helps in

Options

A. Hydrostasis
B. Respiration
C. Sound production
D. All of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Air Bladder**: The air bladder, also known as the swim bladder, is an internal gas-filled organ found in many bony fishes (Osteichthyes). It plays a crucial role in the fish's ability to maintain buoyancy in water.

2. **Function of the Air Bladder**: The primary function of the air bladder is to provide buoyancy. By adjusting the amount of gas in the bladder, fish can control their position in the water column, allowing them to float, sink, or maintain their depth without expending energy.

3. **Hydrostatic Organ**: The air bladder is classified as a hydrostatic organ. This means it helps in maintaining hydrostatic pressure, which is essential for the fish to stay balanced in the water. This is particularly important for bony fishes, as they rely on this organ for stability.

4. **Secondary Functions**: In some species, particularly lungfish, the air bladder can also assist in respiration, allowing the fish to extract oxygen from the air. However, this is not the primary function for most bony fishes.

5. **Analyzing the Options**: The question provides several options: hydrostasis, respiration, sound production, and all of these. Since the main function of the air bladder is to aid in buoyancy (hydrostatics), the best answer among the options is "hydrostasis".

6. **Conclusion**: Therefore, the correct answer to the question "Air bladder in a fish helps in" is "hydrostasis".

**Final Answer**: Hydrostasis.

---