Mutualism
a. ecological relationship between members of two different species that directly interact with each other.
b. ecological, symbiotic relationship in which one species benefits and another is neither nor harmed.
c. ecological, symbiotic relationship between two species that each benefit from their interaction.
d. ecological, symbiotic relationship in which one organism benefits by harming another.

C. Ecological, symbiotic relationship between two species that each benefit from their interaction.

Explanation:

A symbiotic relationship is the ecological relationship in which two distinct species interact to live. This relationship can be either beneficial for species, harmful or does not exert any influence.

Mutualism is a kind of symbiotic relationship. In this relationship the two species lives in close association with each other, in this association both the species receives the benefit to be together.

most community's take hundreds of years to become stable