Bronchioles' structural features determine correct statements Steps:

• Recall bronchioles are small airways lacking cartilage and goblet cells, with smooth muscle and simple epithelium.
• Evaluate statement 1: bronchioles do not contain cartilage, unlike larger bronchi.
• Evaluate statement 2: bronchioles lack goblet cells and submucosal glands, reducing mucus production.
• Confirm statement 3: all bronchioles have smooth muscle for airflow regulation.

Why D is correct:

• Only statement 3 aligns with the anatomical definition of bronchioles as having prominent smooth muscle layers for constriction and dilation.

Why the others are wrong:

• A includes false statements 1 and 2 about cartilage and goblet cells.
• B includes false statement 1 about cartilage.
• C includes false statement 2 about goblet cells.

Final answer: D