If an animal is an herbivore, does that mean it cannot have interactions with organisms other than the plants it eats?

A)No; an herbivore might also have a mutualistic relationship with, for instance, intestinal bacteria.
B)No; an herbivore could be prey in predator/prey interactions.
C)Yes; natural selection predicts a single relationship strategy will eventually emerge with the greatest fitness.
D)both a and b