What is the name of structure that prevents the bony fishes from sinking?

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the name of the structure in bony fishes that prevents them from sinking.

2. **Identifying the Relevant Structure**: In bony fishes, there is a specific organ that helps them maintain buoyancy in water.

3. **Explaining the Function**: This organ is responsible for regulating the fish's buoyancy, allowing them to stay at their desired depth in the water without expending energy.

4. **Naming the Structure**: The structure that prevents bony fishes from sinking is called the **air bladder**.

5. **Describing the Air Bladder**: The air bladder is an internal gas-filled organ that adjusts the fish's buoyancy by changing the amount of gas it contains.

6. **Conclusion**: Therefore, the correct answer to the question is **air bladder**.

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