Which transmission method involves an infectious agent traveling in saliva or mucous?

The correct answer, which describes an infectious agent traveling in saliva or mucous, is droplet transmission. This method occurs when respiratory droplets are expelled from an infected person during actions such as coughing, sneezing, or even talking. These droplets can carry pathogens like viruses and bacteria, potentially infecting someone nearby.

Droplet transmission is distinct because it typically involves shorter distances; the droplets generally fall to the ground within a short range, often less than six feet, limiting the spread. This is different from vehicle transmission, which involves contaminated objects or substances like water or food, and parenteral transmission, which refers to entry through the skin or mucous membranes via needles or other sharp instruments. Direct contact transmission involves physical interaction between an infected individual and another person, without the respiratory droplet mechanism. Thus, droplet transmission specifically pertains to infectious agents spreading through respiratory droplets, making it the correct choice in this context.