The relationship between the 2 species that would be mutually beneficial would be B. A flowering plant and a bee, the bee is able to obtain nutrients and essential necessities by the flower, pollen, and it also helps the flower by transporting the pollen from one flower to that of another one, where pollination can take place.
Well it wouldn’t lead to the development to a completely new species but it would cause the organisms in that are evolved to adapt to their current situations so the answer would be evolution is any at all