Mucus occurs in both the respiratory and digestive tracts. what is its main immunological function? physically trapping of pathogens sweeping away debris destruction of pathogens because it is acidic increasing oxygen absorption

The answer would be: physically trapping of pathogens

Mucus has a high viscosity that could physically trap the pathogens so it could not attack the body cells. In respiratory it could also sweep all the debris because the respiratory epithelial cell has cilia that constantly moves.
It won't help in oxygen absorption, it could disrupting the oxygen absorption instead as it could physically block the air.