The correct option is C It holds good even when the resources are not limiting
Competitive exclusion principle was proposed by Georgy Gause, a Russian biologist. It states that two closely related species competing for the same resources cannot coexist indefinitely and the competitively inferior one will be eliminated eventually. Hence option a and b are correct.
For example, when Paramecium aurelia and Paramecium caudatum are grown individually in the lab, both species manage to thrive. But when they are grown in the same nutrient medium that has limited nutrients, their growth is relatively lesser. Furthermore, Paramecium aurelia (competitively superior) eventually outcompetes Paramecium caudatum. Hence, this principle may be applicable only if the resources are limiting and not otherwise. So option c is incorrect and option d is correct.