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

Competition is an interaction between individuals or species that use the same resources and, as a result, both are negatively affected. In competition, both the competitors try to obtain the same resource, and it becomes limited due to
Their common use. Thus, they experience a reduction in their population size, growth or reproduction.
(1) In parasitism, one partner (parasite) benefits while the other partner (host) is harmed.
(2) In mutualism, both partners benefit from the interaction.
(4) In predation, one partner (predator) benefits, and the other partner (prey) is harmed.