Identify the incorrect statement:

Options

A. The larynx, rings in the wall of trachea and the epiglottis are cartilaginous
B. A negative intrapleural pressure will help in keeping the lungs inflated
C. An airtight thoracic chamber is essential as we can directly alter the pulmonary volume
D. The conducting part of the airway warms, humidifies and filters the air reaching the exchange site

Answer

To identify the incorrect statement from the provided options, we will analyze each statement step by step.

### Step-by-Step Solution:

1. **Examine Option 1**:
- The statement mentions that the larynx and the epiglottis are made of cartilage.
- **Analysis**: This is correct. The larynx, which is involved in sound production, is indeed made of cartilage, as is the epiglottis, which prevents food from entering the trachea during swallowing.

2. **Examine Option 2**:
- This option states that negative intra-pleural pressure helps in keeping the lungs inflated.
- **Analysis**: This statement is also correct. The negative pressure within the pleural cavity is essential for lung inflation during the process of breathing.

3. **Examine Option 3**:
- The statement claims that an airtight thoracic chamber is essential as we can directly alter the pulmonary volume.
- **Analysis**: This statement is incorrect. While the thoracic cavity is airtight, we cannot directly alter the pulmonary volume; changes in pulmonary volume occur indirectly through the expansion and contraction of the thoracic cavity during breathing.

4. **Examine Option 4**:
- This option states that the conducting part of the airways warms, humidifies, and filters the air reaching the exchange site.
- **Analysis**: This statement is correct. The conducting airways (like the trachea and bronchi) do indeed warm, humidify, and filter the air before it reaches the alveoli where gas exchange occurs.

### Conclusion:
Based on the analysis, the incorrect statement is **Option 3**.

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