Harry suffers from cystic fibrosis and frequently has periods where he can hardly breathe. The problem is most likely the result of A)inflammation of the bronchi. B)constriction of the trachea. C)thick secretions that exceed the ability of the respiratory tract cilia to remove them. D)laryngeal spasms that occur in response to a toxic substance produced by the epithelial cells. E)collapse of one or both lungs.