Select the correct option for conducting.system of respiratory system

Options

A. (1) It is noncollapsable part
B. (2) It is the site of actual diffusion oxygen and carbondioxide between blood and atmospheric air
C. (3) it clears the air from foreign particles and humidifies
D. (4) Both 1 and 3

Answer

### Step-by-Step Solution:

1. **Understanding the Conducting System**: The conducting system of the respiratory system includes all the structures that transport air to the sites of gas exchange. This starts from the trachea and includes the bronchi and bronchioles up to the terminal bronchioles.

2. **Identifying the Functions of the Conducting System**: The primary functions of the conducting system are to:
- Filter and clear air from foreign particles.
- Humidify the air.
- Warm the air before it reaches the lungs.

3. **Differentiating Between Conducting and Respiratory Zones**:
- The conducting zone includes the trachea, bronchi, and bronchioles, which do not participate in gas exchange.
- The respiratory zone includes the alveoli and respiratory bronchioles, where gas exchange occurs.

4. **Evaluating the Options**:
- The first option states that the conducting system is a non-collapsible part. This is incorrect because the conducting airways can collapse under certain conditions.
- The second option describes the site for actual diffusion of oxygen and carbon dioxide. This is incorrect as diffusion occurs in the alveoli, which are part of the respiratory zone.
- The third option states that the conducting system clears the air from foreign particles and humidifies it. This is a true statement.

5. **Conclusion**: Based on the evaluation of the options, the correct answer is that the conducting system clears the air from foreign particles and humidifies it.