D - The organisms on the island are slightly different than those on the mainland.
The reason why this is the correct answer is because each successive generation on the mainland as well as the island both develop and continue adapting to their specific ecological niche and environment. They are, howerer, both still part of the same species.
I will have to say D) they keep the prey population low so they will be less likely to deplete resources such as food, water, and shelter... hope i helped!!