Fact 1: Energy enters ecosystems in the form of sunlight or chemical compounds.

Fact 2: Sunlight is the source of light in nature.

Given the two facts above, answer the question "What do ecosystems in nature need an influx of to remain feasible?" with the following options: 
- Continuous nuclear energy.
 - Natural lipids and proteins.
 - Energy.
 - rain
 - water
 - Energy
 - oxygen
 - Renewable Sunny Delight.


 

   Energy.      