During inspiration ,

Options

A. diaphragm contracts and become dome shaped
B. diaphragm contracts and become flat
C. diaphragm relaxes and become dome shaped
D. diaphragm relaxes and become flat

Answer

### Step-by-Step Solution:

1. **Understanding Inspiration**:
- Inspiration, also known as inhalation, is the process of taking air into the lungs. During this process, oxygen is absorbed from the air, and carbon dioxide is expelled from the body.

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

3. **Diaphragm Movement During Inspiration**:
- When we inhale, the diaphragm contracts. This contraction causes the diaphragm to move downward and flatten out, rather than becoming dome-shaped.

4. **Effect on Thoracic Cavity**:
- The contraction of the diaphragm increases the volume of the thoracic cavity. As the volume increases, the pressure within the thoracic cavity decreases (intra-alveolar pressure).

5. **Airflow into the Lungs**:
- Due to the decrease in pressure inside the thoracic cavity, air from the atmosphere is drawn into the lungs to equalize the pressure, allowing for the intake of oxygen.

6. **Conclusion**:
- Therefore, during inspiration, the diaphragm contracts and becomes flat. This makes option 2 ("diaphragm contracts and becomes flat") the correct answer.

### Final Answer:
**The correct answer is: Diaphragm contracts and becomes flat.**

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