Answer:
The correct answer to the question: Cells lining the human respiratory tract have projections that help keep the passageway clean, moving debris and mucus up and out. These cellular projections are:__, would be, A: Cilia.
Step-by-step explanation:
The human respiratory system is not just a set of tubes, and a pair of lungs, where the exchange of gases for life, takes place. Because air carries with it much more than just gases, like oxygen, but it also carries microorganisms, and damaging particles, the respiratory system has in place a series of physiological, and organic mechanisms, to protect us from these damaging elements in air. One such protection lines are the projections present in the cells that are present all along the linings of the respiratory tubes. These projections are like small hairs, that constantly move like a brush, to remove elements from the air that should not be present in the lungs. These brush-like projections are called cilia.