In ecology there are several types of interactions, that can be described in terms of how they affect each part, this being positively, negatively, or neutrally.
When the interaction has a positive outcome for both organisms involved, then we can talk about mutualism.
Let's take a look at each of the interactions given:
a) Coyote and pocket mouse: In this case, the coyote is the predator and the pocket mouse is the prey, so no mutual benefit here.
b) Bigeye trevally and bottlenose dolphin: Here, both organisms compete for the same resources, there is mutual harm.
c) Leaf-cutter ant and fungus: The ants cultivate and protect the fungus and also feed on it, so there is mutual benefit for both species.
d) Yucca plant and yucca moth: The moth pollinates the yucca plant and also feeds on the yucca plant, so this is also a case of mutual benefit.
e) Giant armadillo and leaf-cutter ant. Here we have another case of predator and prey, so there is no mutual benefit.
So, the cases with mutual benefit are the Leaf-cutter ant and fungus, and the yucca plant and yucca moth.
