What Do These Results Suggest About the Importance of Biodiversity

What do these results suggest about the importance of biodiversity in an ecosystem?

A) That genetic diversity is not important as long as there are enough species around to replace those that don't survive
B) That genetic diversity is not important because species cannot survive large environmental changes
C) Biodiversity is important because the larger a population, the more likely a few will survive any environmental change
D) That genetic diversity is necessary for an ecosystem to respond to environmental changes