You are presented with the question "Energy enters ecosystems in the form of " and the following answer choices: 
- wind
 - warmth
 - light
 - glucose
 - photons
 - sun's heat
 - heat
 - expelled

Now knowing that energy enters ecosystems in the form of sunlight or chemical compounds and sunlight is composed of photons, or particles of solar energy, choose the best answer.


 

     photons    