This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Surgery
Metaplasia is thought to be caused in most cases by:- 
Select and explain. 
A. Genetic mutation, B. Oncogenic virus, C. Chronic irritation, D. Immunologic reaction
C: Chronic irritation
Answer: C: Chronic irritation 
Explanation: Chronic irritation Metaplasia is commonly seen in the epithelial surfaces of the bronchial tree secondary to chronic irritation of cigarette smoke. Metaplasia may also be seen in areas of long-standing, chronic infections.