What part of the respiratory system prevents the air-passage from collapsing?

The correct answer is: (B) Rings of cartilage

Rings of cartilage are present in the trachea. These C-shaped cartilaginous rings keep the air passage open and prevent it from collapsing during breathing.

• Cartilage is flexible yet strong, supporting the airway.
• The trachea has about 16–20 C-shaped rings.
• These rings allow smooth airflow into lungs.
• They also protect the trachea from external pressure.
• Bronchi also contain smaller cartilaginous plates.

• Ribs protect lungs but do not prevent airway collapse.
• Spine supports the body structure, not the air passage.