Which statement may be used to defi ne a bronchiole? A. They are the airways that branch from the left and right primary bronchi. B. They are kept open by “C” shaped rings of cartilage. C. Their walls have supporting cartilage between smooth muscle. D. Their walls contain smooth muscle but no cartilage.
Option D. Bronchioles vary from all the bigger airways in having no sup- porting cartilage. They do have smooth muscle.
