In birds, the lungs are

Options

A. Spongy
B. Spongy and inelastic
C. Solid
D. Solid and elastic

Answer

### Step-by-Step Solution:

1. **Understanding the Structure of Bird Lungs**:
- In birds, the lungs are specialized organs that are different from those of mammals. They are not solid but rather have a unique structure.

2. **Identifying the Nature of Bird Lungs**:
- The lungs of birds are described as "spongy." This means they have a porous structure that allows for gas exchange.

3. **Elasticity of Bird Lungs**:
- Unlike mammalian lungs, which are elastic and can change shape during breathing, bird lungs are "inelastic." This means they do not change their shape or size when breathing.

4. **Function of Air Sacs**:
- Birds have additional structures called air sacs that work in conjunction with the lungs. These air sacs help in the movement of air through the lungs but do not change the size of the lungs themselves.

5. **Conclusion**:
- Based on the characteristics of bird lungs, the correct description is that they are "spongy and inelastic."

### Final Answer:
- In birds, the lungs are **spongy and inelastic**.