Which of These Does NOT Provide a Physical or Chemical

Question

Which of these does NOT provide a physical or chemical barrier?
A) macrophages
B) saliva
C) urine
D) mucus
E) stratified squamous epithelium

Accepted Answer

Macrophages are immune cells that engulf and digest pathogens, but they do not act as a physical or chemical barrier. The other options provide barriers to prevent pathogen entry.