The correct answer is kills the cilia in the upper respiratory tract.Concept:Health:According to WHO (World Health Organization), Å“Health is a state of complete physical, mental, and social well-being and not merely the absence of disease or infirmity.There are many factors that affect health, such as:Poor dietGenetic disordersStress, and anxietyInfection from pathogensIntake of unhealthy and unhygienic foodLack of exercise and other physical activities.Drug abuse Explanation:Harmful effects of smoking:?Cigarette smoking can cause immediate damage to our health.Each puff of cigarette smoke contains a mix of over 7,000 chemicals.When the smoke enters the body it first destroys the cilia, the tiny hairs in the airway that keep dirt and mucus out of the lungs.The smoke then enters the lungs and mixes with the blood that is then carried to the rest of our body contains these toxic chemicals.Tobacco smoke contains carbon monoxide, this deadly gas displaces the oxygen in the blood, depriving the organs of the oxygen they need. Smoking can cause irreversible damage to elastin, the protein that provides the lungs with elasticity. Thus, affecting the breathing efficiency of the lungs. Furthermore,the long term effect of smoking can be seen in the form of lung cancer. In addition to lung cancer, smoking can lead to other respiratory cancers, such as:The oropharynx (the back of the mouth, including parts of the tongue, the soft palate, the side and back of the throat, and the tonsils)Larynx (the Å“voice box)Trachea (the Å“windpipe)Bronchus (one of two large airways that connect the trachea to the lungs)Since cilia are the first part of the body to be adversely affected by the smoke, it is the primary reason that smoking cigarettes is bad for our health.