P: coughing; C: saliva; B: complement system. That is option B.
What are immune barriers?
The immune barriers are defined as those natural barriers that helps to prevent the invading of microorganisms on a host cell.
The physical barrier are natural structural obstacles example is coughing.
The Chemical barrier is the saliva that contains enzymes which can digest invading microorganisms.
The biological barrier is the complement system.
Learn more about immune system here:
https://brainly.com/question/15595309
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