Mark the true statement among the following with reference to normal breathing.

Options

A. Inspiration is a passive process whereas expiration is active.
B. Inspiration is an active proces whereas expiration is passive.
C. Inspiration and expiration are active processes.
D. Inspiration and expiration are passive processes.

Explanation

To determine the true statement regarding normal breathing, we need to analyze the processes of inspiration and expiration.

### Step-by-Step Solution:

1. **Understand the Process of Inspiration**:
- Inspiration is the process of taking air into the lungs.
- It involves the contraction of the diaphragm and intercostal muscles, which expand the thoracic cavity and decrease the pressure inside the lungs, allowing air to flow in.
- This process requires energy, making it an active process.

2. **Understand the Process of Expiration**:
- Expiration is the process of expelling air from the lungs.
- It primarily occurs when the diaphragm and intercostal muscles relax, allowing the thoracic cavity to decrease in volume and increase the pressure in the lungs, pushing air out.
- This process is generally passive, as it does not require energy; it relies on the natural elasticity of the lungs and thoracic cavity.

3. **Evaluate the Statements**:
- **Statement 1**: "Inspiration is a passive process whereas expiration is the active." - This is false.
- **Statement 2**: "Inspiration is an active process whereas expiration is passive." - This is true.
- **Statement 3**: "Both inspiration and expiration are active processes." - This is false.
- **Statement 4**: "Both inspiration and expiration are passive processes." - This is false.

4. **Conclusion**:
- The true statement among the options is: "Inspiration is an active process whereas expiration is passive."