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

Options

A. Inspiration is a passive process where as expiration is active
B. Inspiration is a active process where as expiration is passive
C. Inspiration and expiration are active pro- cesses
D. Inspiration and expiration are passive processes

Answer

To solve the question regarding normal breathing, we need to analyze each of the given options and determine which statement is true based on our understanding of the respiratory process.

### Step-by-Step Solution:

1. **Understanding Inspiration**:
- Inspiration is the process where fresh air enters the lungs, specifically the alveoli.
- This process requires the contraction of the diaphragm and intercostal muscles, which actively expands the thoracic cavity and lowers the pressure inside the lungs, allowing air to flow in.

2. **Understanding Expiration**:
- Expiration is the process where stale air is expelled from the lungs.
- This process is generally passive during normal breathing. It occurs when the diaphragm and intercostal muscles relax, allowing the elastic recoil of the lungs to push air out.

3. **Analyzing the Options**:
- **Option A**: "Inspiration is a passive process whereas expiration is active."
- This is incorrect because inspiration is an active process.
- **Option B**: "Inspiration is an active process whereas expiration is passive."
- This is correct as per our understanding of the processes involved in breathing.
- **Option C**: "Inspiration and expiration are active processes."
- This is incorrect because expiration is typically a passive process.
- **Option D**: "Inspiration and expiration are passive processes."
- This is incorrect because inspiration is an active process.

4. **Conclusion**:
- Based on the analysis, the true statement regarding normal breathing is **Option B**: "Inspiration is an active process whereas expiration is passive."

### Final Answer:
**Option B**: Inspiration is an active process whereas expiration is passive.