<prompt> Chronic bronchitis can be a premalignant condition, which involves:Columnar to squamousSquamous to columnarSquamous to cuboidalCuboidal to squamous  <response>: Ans. a Columnar to squamousRef: Robbins 9thpg 679Chronic bronchitis is an example of squamous metaplasia in which normal columnar epithelium of respiratory tract is replaced by squamous epithelium; 