Answer: Metaplasia
Explanation: The process of substituting cells in the trachea with cells that can survive the harsh effect from smoking. This process is called Metaplasia.
Metaplasia is a form of Cellular adaptation process, which initiate response to different types of stimuli and adverse changes in the environment.
Metaplasia involves changing epithelial cells (which lines all the body parts) to another cells that can resist the adverse effects from the extrinsic environment.
