Out of the choices given, the one that is true for two different species that have a competitive relationship in the same ecosystem is they share the same niche. The correct answer is C.
Niche can be defined as a specific area for an organism where it inhabits and shows interactions with environment for their survival in terms of resources. If two species share the same niche then they will have competitive relationship for sometime.
It is because according to the competitive exclusion principle, it is not possible for two species to share the same niche a longer duration of time. Thus, out of these two competitive species one will survive while the other specie will migrate or eliminate.
