During expiration, the diaphragm becomes

Options

A. normal
B. oblique
C. flatttened
D. dome shapped

Answer

### Step-by-Step Solution:

1. **Understanding the Breathing Process**: Breathing involves two main phases: inspiration (inhaling) and expiration (exhaling). During inspiration, air enters the lungs, while during expiration, air is expelled from the lungs.

2. **Role of the Diaphragm**: The diaphragm is a dome-shaped muscle located below the lungs. It plays a crucial role in the mechanics of breathing.

3. **Diaphragm during Inspiration**: When we inhale, the diaphragm contracts and flattens. This contraction increases the volume of the thoracic cavity, creating a pressure difference that allows air to flow into the lungs.

4. **Diaphragm during Expiration**: In contrast, during expiration, the diaphragm relaxes. This relaxation allows the diaphragm to return to its original dome shape. The decrease in thoracic cavity volume increases the pressure in the lungs, forcing air out.

5. **Conclusion**: Therefore, during expiration, the diaphragm becomes dome-shaped again after relaxing from its flattened state during inspiration.

### Final Answer:
During expiration, the diaphragm becomes **dome-shaped**.

---