To which type of barriers under innate immunity, do the saliva in the mouth

To which type of barriers under innate immunity, do the saliva in the mouth and the tears from the eyes belong?

(a) Cytokine barriers
(b) Cellular barriers
(c) Physiological barriers
(d) Physical barriers

Physiological barriers

This type of barriers under innate immunity, i.e. saliva in the mouth and the tears from the eyes.

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