A long-term smoker's bronchial epithelium undergoes a change from pseudostratified columnar to stratified squamous epithelium. This cellular adaptation is best described as which of the following?

✓ Correct Answer: Option B

Metaplasia is a reversible change in which one adult cell type is replaced by another adult cell type. In smokers, the more delicate columnar epithelium is replaced by tougher squamous epithelium, which is better able to withstand chronic irritation.