I believe the best answer for this is B. The variety of ecosystems found on the islands.
Plants get nitrogen from the soil but it has to be turned into nitrates (by lighting or nitrogen fixation); this because nitrogen in the air is very unreactive, Then the animal eats the plant.
Bacteria can get nitrogen simply from the air
All stem cells—regardless of their source—have three general properties: they are capable of dividing and renewing themselves for long periods; they are unspecialized; and they can give rise to specialized cell types. Stem cells are capable of dividing and renewing themselves for long periods.
