What are the main components needed to insure ecosystem stability?

a. estuary, savanna, and tundra

b. primary and secondary succession

c. food, water, shelter and biodiversity

d. moderate climate, sufficient space, and adequate sunlight

The correct answer should be d. moderate climate, sufficient space, and adequate sunlight

No organism can exist without the sun, while a moderate climate is necessary for the establishment of a stable ecosystem. Sufficient space prevents overpopulation which later prevents other nasty things.