In which of the following interactions, both partners are adversely affected?

Mutualism (Symbiosis) is a relationship, in which both the interacting organisms/partners are benefited from each other. Predation is the consumption of one species (the prey) by another (the predator). Parasitism is a host -parasite relationship in which one (parasite) is benefited while other (host) is adversely affected, although not necessarily killed. Competition is the injurious effect of one organism on another because of the removal of some resource of the environment. This phenomenon can result in major fluctuations in the composition of the microbial population in the soil.