What Prevents Pathogens from Entering Our Bodies Through the Delicate

What prevents pathogens from entering our bodies through the delicate tissues of the lungs?

A) The lining of the lungs has a low pH that creates an inhospitable environment for most pathogens.
B) The tubes entering the lungs are lined with mucus that traps pathogens and is then removed from the respiratory system.
C) The cells of the lungs are covered by several layers of dead cells that prevent pathogens from getting to living lung tissue.
D) Certain cells in the lungs produce toxins that paralyze pathogens before they can infect the body.