The answer is P: coughing; C: saliva; B: complement system.
Coughing is a physical immune response because it mechanically (physically) removes irritants and pathogens from the lungs. Sneezing is also the physical immune response.
Saliva is a chemical immune response because it contains different enzymes able to break down pathogens.
Complement system is a biological immune response because it activates biological molecules, such as antibodies, to remove pathogens from the organism.
