Correct answer: A). Competitive exclusion.
The competitive exclusion principle states that the two species that are competing for the same resources can not live together.
One out of the two competitors will always have an advantage over the other, that leads to the extinction of another species. As a result of that competing species evolve different characteristics in the areas where both of them coexist. Rest all parasitism, mutualism, and commensalism is an example of the symbiotic relationship.
Hence, the correct answer would be option A.