Final answer:
(A) Commensalism is the ecological interaction in which one species is helped and the other is neither helped nor hurt, unlike mutualism or parasitism.
Step-by-step explanation:
An ecological interaction in which one species benefits while the other is neither helped nor hurt is known as commensalism. This type of symbiotic relationship can involve various forms of interactions. For example, birds nesting in trees represent a commensal relationship where the birds benefit from the shelter the tree provides, while the tree is neither harmed nor helped by the presence of the nests.
Another example is mites hitching a ride on larger insects, where the mites gain mobility without affecting the insects. Unlike mutualism, where both species benefit, or parasitism, where one species benefits at the expense of the other, commensalism reflects a relationship that is neutral for one party.