Answer:
b. smoking can paralyze the ciliary escalator.
Explanation
Generally cilia in the respiratory tract of smoker will undergo paralysis for 1-3 hours after smoking, and generally paralyzed in chronic smokers.
This is because the toxins( the TAR) in the cigarette destroy the mucocilliary escalator that trapped inhaled pathogens in air as it passes through the bronchi and push them up with phlegm out of the respiratory tract.
Therefore ,with the loss of cilirary function, pathogens are retained in the lungs leading to respiratory tract infections