Character displacement involves different populations of the same species or what had been the same species evolving to use resources not used by the other population. This can help separate or keep separate populations in the same place (sympatric).
Work Step by Step
To get to this answer, first look at the definition of character displacement--it involves sympatric species/populations which are selected to use different resources. Then apply this to the idea of sympatric species: how would this keep species in the same place (sympatric) from interbreeding and becoming one hybrid species.