This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Obstructive Lung Disease, Subject name: Pathology
Which of the following statement are true regarding pathogenesis of bronchitis? 
Select and explain. 
A. Initiating factor is exposure to noxious stimuli or tobacco, B. Hypersecretion of mucus in large airways, C. Inflammatory infiltrate, D. All of the above
D: All of the above
Answer: D: All of the above 
Explanation: Chronic Bronchitis The primary or initiating factor is exposure to noxious or irritating inhaled substances such as tobacco smoke (90% of patients are smokers) and dust from grain, cotton, and silica. Earliest feature is hypersecretion of mucus in the large airways, associated with hyperophy of the submucosal glands in the trachea and bronchi. Inhalants that induce chronic bronchitis cause cellular damage, eliciting both acute and chronic inflammatory responses