Which are correct examples of physical (P), chemical (C), and biological (B) barriers?
P: complement system; C: saliva; B: coughing
P: coughing; C: saliva; B: complement system
P: coughing; C: sneezing; B: complement system
P: complement system; C: saliva; B: sneezing
The correct examples are:
P: complement system; C: saliva; B: coughing