<em>Examples of a nonspecific external response to infectious agents and harmful bacteria are the following;</em>
Mucus, saliva, and tears.
They are nonspecific external responses that help to prevent pathogens from entering our bodies.
The specifics contain types of enzymes that break down the bacterial cell walls. An external response of Mucus tends to trap pathogens as well.
Crease, could you mark brainliest? :)
The correct answer to this question is this one: they lacked oxygen. The earliest organisms were completely heterotrophic in nature because of the reason that they lacked oxygen. <span>A heterotroph is an organism that cannot fix carbon and uses organic carbon for growth. </span>