You are presented with the question "the basic necessity of an ecosystem enters in the form of what?" and the following answer choices: 
- heat
 - recycling
 - trees
 - food
 - sunlight
 - adding heat
 - movement
 - root growth

Now knowing that energy enters ecosystems in the form of sunlight or chemical compounds and energy is a basic necessity of an ecosystem, choose the best answer.


 

     sunlight    