A chronic smoker's bronchial epithelium undergoes a reversible change where ciliated columnar cells are replaced by stratified squamous cells. This cellular adaptation is best described as:

✓ Correct Answer: Option B

Metaplasia is the reversible change of one differentiated cell type to another differentiated cell type, typically in response to chronic irritation or stress. In smokers, the pseudostratified columnar epithelium of the bronchi is replaced by more resilient stratified squamous epithelium.