Lung fishes have

Options

A. Uncovered well developed gills
B. Covered well developed gills
C. Reduced but covered gills
D. Air bladder

Answer

### Step-by-Step Solution:

1. **Understanding Lung Fishes**: Lung fishes belong to a group of fish that possess both gills and lungs, allowing them to respire in different environments. They are known for their ability to survive in low water conditions by utilizing their lungs.

2. **Respiration Mechanism**: In normal aquatic conditions, lung fishes primarily respire through their gills. However, when the water levels are low or when they are in a stagnant environment, they can switch to breathing air using their lungs.

3. **Evaluating Options**:
- **Option A: Uncovered well-developed gills**: This is incorrect because lung fishes do not have uncovered well-developed gills; they have gills that are adapted for their dual respiratory system.
- **Option B: Covered well-developed gills**: This is also incorrect. Lung fishes do not have covered well-developed gills.
- **Option C: Reduced but covered gills**: This option is incorrect as well. While lung fishes may have reduced gills, they are not necessarily covered.
- **Option D: Air bladder**: This is the correct answer. Lung fishes have an air bladder that is modified for gaseous exchange, allowing them to breathe air when necessary.

4. **Conclusion**: The correct answer to the question "Lung fishes have" is **Option D: Air bladder**. This adaptation is crucial for their survival in varying aquatic conditions.