What is the function of the conducting airways?

• A. Gas exchange occurs here.
• B. They filter chemicals and other harmful substances in the air.
• C. They are the site of alveolar diffusion.
• D. They supply oxygen to the blood.

Answer: (B)

The conducting airways are responsible for moving air into the lungs while conditioning and protecting the lower airways. Their main role is to filter chemicals and other harmful substances in the air through mucus and cilia, which trap particles and drive them out of the respiratory tract. This clearance prevents irritants and pathogens from reaching the delicate gas-exchange surfaces. Gas exchange, by contrast, happens in the alveoli, not in the conducting airways, and oxygen transfer to the blood occurs there after diffusion. So the key function described is filtering harmful substances from the inhaled air.