You are presented with the quiz "Production of ethanol is dependent  on " 

But you don't know the answer, so you turn to your teacher to ask for hints. He says that "ethanol is produced by alcoholic fermentation of the glucose in corn or other plants" and "plants use the sun's energy to transform carbon dioxide gas and water into a sugar called glucose". 

So, what's the best answer to the question?


 

  the sun's energy         