Q: Fact 1: Energy enters ecosystems in the form of sunlight or chemical compounds. Fact 2: Energy is a basic necessity of an ecosystem. Given the two facts above, the basic necessity of an ecosystem enters in the form of what?

Pick your answer from:
(A). heat.
(B). recycling.
(C). trees.
(D). food.
(E). sunlight.
(F). adding heat.
(G). movement.
(H). root growth.
A:
(E).