which type of barrier are coughing and sneezing?\npsychological\nchemical\nbiological\nphysical

Brief Explanations:

Coughing and sneezing expel foreign - substances physically from the body. They are physical responses to clear the respiratory tract of irritants, pathogens etc. They are not psychological (related to mental processes), chemical (involving chemical substances like enzymes or antibodies), or biological (in the sense of cellular or molecular biological mechanisms).

Answer:

physical