Question

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

Explanation:

To solve this, we analyze each type of barrier:

• Physical (P) barriers: These are mechanical actions to remove pathogens. Coughing is a physical action to expel microbes, so P should be coughing.
• Chemical (C) barriers: These involve chemical substances. Saliva contains enzymes (like lysozyme) that act as a chemical defense, so C should be saliva.
• Biological (B) barriers: These involve biological components of the immune system. The complement system is a biological (immune) component, so B should be the complement system.

Now we check the options:

• First option: P (complement system - wrong, it's biological), C (saliva - correct), B (coughing - wrong, it's physical) → Incorrect.
• Second option: P (coughing - correct), C (saliva - correct), B (complement system - correct) → Matches our analysis.
• Third option: P (coughing - correct), C (sneezing - wrong, sneezing is physical), B (complement system - correct) → Incorrect.
• Fourth option: P (complement system - wrong), C (saliva - correct), B (sneezing - wrong, physical) → Incorrect.

Answer:

B. P: coughing; C: saliva; B: complement system