Bronchioles' structural features

Steps:

• Identify key structures in bronchioles: no cartilage, but present are smooth muscle and cilia.
• Statement 1 likely refers to cartilage (absent in bronchioles).
• Statement 2 refers to smooth muscle (present for contraction).
• Statement 3 refers to ciliated epithelium (present for mucus clearance).
• Select option matching 2 and 3 only.

Why D is correct:

• Bronchioles contain smooth muscle and ciliated cells but lack cartilage, per respiratory anatomy definitions.

Why the others are wrong:

• A includes 1 (cartilage), absent in bronchioles.
• B excludes 3 (cilia), which are present.
• C includes 1 (cartilage), absent in bronchioles.

Final answer: D