Why Do Cigarette Smokers Cough More Than Nonsmokers

Why do cigarette smokers cough more than nonsmokers?

A) The tar in cigarette smoke tends to make alveoli stick together, and coughing separates them.
B) Cigarette smoke harms the cilia that normally move debris out of the lungs, and coughing is the remaining way to clean the lungs.
C) Cigarette smoking partially paralyzes the muscles in the lungs, resulting in an increased residual volume, and coughing exchanges this "dead air."
D) By raising the pressure in the lungs, coughing forces more oxygen into the blood.