The correct answer is: B. symbiosis when the interaction is useful to both the populations
Symbiosis is a close relationship between two different species that live together. There are three types of symbiosis: mutualism, commensalism, and parasitism.
In mutualism, both species benefit from the relationship. For example, some plants have bacteria that live in their roots and help them to fix nitrogen from the air. The bacteria get a place to live and food, and the plant gets nitrogen that it needs to grow.
In commensalism, one species benefits from the relationship, while the other species is not affected. For example, barnacles often attach themselves to whales. The barnacles get a place to live and food, while the whale is not harmed by the barnacles.
In parasitism, one species benefits from the relationship, while the other species is harmed. For example, tapeworms live in the intestines of animals. The tapeworms get food from the animal’s food, while the animal is harmed by the tapeworms.
In the question, the interaction is useful to both the populations. This is an example of mutualism.