A patient with COPD undergoes metaplasia of respiratory cells. What type of cell do lung cells change to?

In COPD (especially associated with smoking), the normal PSEUDOSTRATIFIED CILIATED COLUMNAR EPITHELIUM of the bronchi undergoes SQUAMOUS METAPLASIA — it transforms into STRATIFIED SQUAMOUS NON-KERATINIZED EPITHELIUM. This is the body's protective response to chronic irritation (similar to Barrett's esophagus being columnar → columnar, but in airways it's columnar → squamous). Keratinized epithelium (B) would be skin-type, not seen internally. A is correct.