Cartilage supports airways in trachea and bronchi

Steps:

• The gas exchange system includes trachea, bronchi, bronchioles, and alveoli.
• Cartilage provides rigid support to larger airways to prevent collapse during breathing.
• Trachea contains C-shaped cartilage rings for structural integrity.
• Bronchi have irregular cartilage plates, while bronchioles lack cartilage and rely on smooth muscle.

Why D is correct:

• In respiratory anatomy, cartilage is defined as present in trachea (rings) and bronchi (plates) to maintain open passages for air flow.

Why the others are wrong:

• A: Excludes trachea, which has essential cartilage rings.
• B: Excludes bronchi, which contain supportive cartilage plates.
• C: Includes bronchioles, which have no cartilage and are too small for rigid support.

Final answer: D