In this task, you are given two facts, and a multiple-choice question. Based on the given facts, answer the question with index of the correct option (e.g, "A").

Fact1: Energy enters ecosystems in the form of sunlight or chemical compounds., Fact2: Energy is a basic necessity of an ecosystem., Question: the basic necessity of an ecosystem enters in the form of what? (A) heat (B) recycling (C) trees (D) food (E) sunlight (F) adding heat (G) movement (H) root growth
E